Exceptions to Urban Reconversion: Double Marginality of Informally Originated Urban Areas in Lisbon Metropolitan Area

Abstract

This article explores the persistent exclusion of certain informal settlements in Portugal from legal urban recognition, focusing on areas characterized by both historical informality and current legal invisibility, here termed by “doubly marginal”. Despite the existence of legal frameworks aimed at integrating Informally Originated Urban Areas (AUGIs), a significant number remain outside the scope of regularization, revealing deep-rooted structural, social, and legal constraints. These cases exemplify the systemic limitations of existing urban governance models and underscore the inadequacy of one-size-fits-all planning laws. By proposing a conceptual typology grounded in social, legal, and environmental dimensions, the article exposes how overlapping vulnerabilities perpetuate urban marginality. The findings point to a critical mismatch between legal norms and the lived realities of affected communities, many of which face barriers that existing legislation is ill-equipped to resolve. The article advocates for a more comprehensive legal framework that responds to the diversity and complexity of informal settlements, particularly in municipalities with limited administrative capacity. This reconceptualization challenges dominant paradigms in urban policy and calls for a rethinking of territorial justice and the right to remain in place.

1. Introduction

In recent decades, informal urbanization has become one of the clearest expressions of the structural inability of the state to ensure effective land management and inclusive housing policy. In Portugal, Informally Originated Urban Areas (AUGIs) reflect this institutional fragility because they emerged from unregulated land subdivision operations, frequently carried out without proper planning permissions, and have proliferated especially on the outskirts of metropolitan areas under demographic pressure, housing shortages, and weak urban oversight.

This phenomenon cannot be fully understood as merely a legal anomaly. It must be seen as a systemic response to structural housing deficits, particularly from the 1960s to the 1980s. During this period, thousands of households resorted to informal solutions as a way to access affordable housing near employment centers, in the absence of effective public housing policy or affordable private supply [1]. The growth of these settlements was further enabled by the permissive or ambiguous role of local authorities, who tolerated or indirectly supported self-built urbanization due to limited enforcement tools or political considerations.

It is also important to emphasize that these AUGIs do not refer to places of precarious housing built with temporary materials, but rather to well-established residential structures aimed at the middle class with some economic capacity that could not find suitable housing solutions on the market. To address this widespread phenomenon, the Portuguese legislator introduced an exceptional and transitional legal framework in 1995 (Law No. 91/95 of 2 September). This law aimed to enable the urban regularization of AUGIs through formal planning instruments such as allotment operations and detailed plans. Originally conceived as a temporary solution to a historically specific urban problem, the law was successively amended and progressively absorbed into the broader territorial planning regime, culminating in its consolidation as Law No. 70/2015 of 16 July.

This revised legislation introduced procedural innovations and expanded the responsibilities of municipalities, including deadlines for the creation of joint administrative commissions and for issuing regularization titles. However, it also introduced a rigid legal architecture, built around narrowly defined eligibility criteria, cumulative procedural requirements, and highly specific implementation.

As a result, many areas, despite being socially consolidated and physically integrated into the urban fabric, have remained outside the scope of legal regularization due to technical constraints, legal ambiguities, environmental limitations, or social vulnerability.

Among the most affected are those territories defined under Article 48 of Law No. 70/2015 as “insusceptible of regularization”, often due to environmental protection regimes, exposure to natural hazards, or conflict with infrastructure easements. As [1] highlights, the legal classification of these areas results not only in exclusion from planning tools but also in the absence of any clear compensatory mechanism, leaving residents in a prolonged state of legal and spatial limbo.

It is within this evolving legal and urban landscape that we propose the concept of “double marginality”. This term captures the condition of AUGIs that, in addition to having originated outside formal urban planning processes, is now legally invisible under current norms. These are cases that either do not fulfil the formal conditions set out in Article 1 of Law No. 70/2015 (such as land classification or licensing timeline), or that fail to meet operational conditions (e.g., lack of formal administration, unresolved land tenure, or spatial insusceptibility). These doubly informal areas thus embody a form of legal liminality, where decades of de facto urban life coexist with a persistent absence of legal recognition. This condition was repeated in many Municipal Master Plans (PDMs), where the classification of insusceptible to regularization had a significant impact.

Against this backdrop, the main objective of this article is to develop a typology of exceptional cases within the AUGI regularization framework, specifically those that illustrate conditions of “double marginality”, where historical informality is compounded by contemporary legal exclusion. These are not isolated anomalies, but structurally embedded situations that expose the limits of the current legal regime and challenge the prevailing models of urban governance.

To achieve this, the article adopts a multi-method approach that combines:

• Documentary and legal analysis of national and municipal frameworks (including Law No. 70/2015 and relevant planning instruments);
• Empirical case studies of selected AUGIs in the Lisbon Metropolitan Area (LMA), representing a range of social, legal, and environmental conditions;
• And spatial analysis and mapping, which visualizes the overlapping vulnerabilities and legal constraints affecting these areas.

The proposed typology is organized along three structuring dimensions: social–demographic; legal–political; environmental–risk factors and is informed by real-world examples of areas that remain legally unresolved despite long-term urban consolidation.

By articulating the systemic obstacles that prevent these territories from achieving legal recognition, this article addresses an existing lacuna in the literature and in public policy by bridging legal analysis and empirical typology, offering a grounded framework for classifying and understanding these exceptional situations. This framework not only enhances our understanding of informal urbanization in Portugal but also provides actionable insights for policymakers. Ultimately, the article advances policy and legal recommendations aimed at constructing a more inclusive and context-sensitive framework for the regularization of informal urban areas, ensuring that future interventions are both equitable and aligned with the lived realities of these territories.

2. Literature Review

2.1. Informal Urbanization and Portuguese Context

The phenomenon of informal urbanization has been widely studied across disciplines, particularly in contexts where rapid urban growth outpaces institutional capacity. Internationally, scholars have explored informal settlements in Latin America, South Asia, and Sub-Saharan Africa, emphasizing the intersections between land tenure insecurity, social inequality, and weak urban governance [2,3]. In European contexts, informal urban development has received comparatively less attention, yet southern countries like Spain, Italy, Greece and Portugal exhibit long-standing traditions of informal land occupation and housing self-production [4,5]. In Italy [6] and Greece [7] for example, informal suburbanization processes have produced peripheral settlements that persist under legal ambiguity, often tolerated by local authorities or addressed through ad hoc amnesties. These parallels underscore the broader European relevance of Portugal’s experience and support the need for comparative legal and policy approaches.

The problem has never been fully addressed, leading to ongoing challenges in urban planning and service provision. Informal settlements often lack essential infrastructure, exacerbating social inequalities and limiting residents’ quality of life. Addressing these issues requires a multifaceted approach that includes enhancing municipal capacities, improving legal frameworks, and fostering community participation in urban planning processes.

Ultimately, fostering community participation is crucial for developing inclusive urban planning strategies that can effectively address the complexities of informal settlements and enhance residents’ living conditions. This approach not only empowers residents but also promotes self-organization, which is vital for the incremental transformation of informal settlements into more sustainable living environments. This transformation often hinges on the recognition of residents’ rights and the integration of their knowledge in shaping urban policies that reflect their needs and aspirations.

In Portugal, AUGIs represent a specific form of informal urbanization characterized by legally unrecognized land subdivision and construction. These areas are often the result of land speculation, lack of public housing alternatives, and permissive attitudes from local authorities, particularly during the urban expansion of the 1960s–1980s. While the enactment of Law No. 91/95 and its subsequent amendments, culminating in Law No. 70/2015, provided a legal framework for urban regularization, numerous limitations remain in practice. These limitations include bureaucratic inefficiencies, lack of political will, and inadequate resources to implement regularization processes effectively, which continue to hinder meaningful progress in addressing informal urbanization challenges in Portugal [8,9].

Despite these challenges, ongoing efforts to refine legal frameworks and enhance governance mechanisms may facilitate the gradual formalization of AUGIs, ultimately improving urban integration and living conditions for affected residents. Enhancing local governance capacity and fostering community engagement are essential steps towards addressing the complexities of informal urbanization in Portugal and ensuring sustainable urban development. This necessitates a collaborative approach that bridges the gap between formal regulations and the realities faced by residents, ensuring that their voices are integral to the planning process [10].

2.2. Informality as a Historical and Structural Condition

In the Portuguese context, urban informality has been historically linked not to illegality in the criminal sense, but to systemic governance failure, a condition that emerged at the intersection of state inaction, market exclusion, and popular strategies for accessing housing. Studies on the genesis of AUGIs in the Lisbon region have shown that the expansion of informal settlements was not merely tolerated but often implicitly supported by local authorities who lacked technical or political resources to oppose them [1]. These settlements provided functional housing solutions at a time when public housing supply was insufficient, and the private market was inaccessible to most working-class families. Informality, in this context, became a normalized mode of urban production, shaping the periphery of Lisbon and other metropolitan areas. There were attempts to counter this process, notably with the approval of Decree-Law No. 46673 of 1965 and later Decree-Law No. 9/73, which sought to regulate urban land subdivision and speed up licensing. However, the lack of technical capacity of local authorities and delays in administrative procedures severely limited their effectiveness. These laws sought to curb illegal urban development, but in practice, they did little to halt a process that was already deeply entrenched. This outcome reflects not only legal gaps but also the bureaucratic complexity and limited capacity of local institutions to implement existing rules, turning regulation into a barrier rather than a solution.

Recent studies point to significant inconsistencies in how municipalities interpret and apply the legal provisions for AUGIs, leading to highly unequal outcomes [11,12]. Additionally, some authors have noted that the legal model depends heavily on resident initiative and collective administration, a model that excludes vulnerable populations, particularly the elderly, low-income households, or those lacking legal ownership documentation [13]. Furthermore, environmental constraints and public land protections often place these areas in a legal limbo, impeding any progress toward formalization.

This legal ambiguity underscores the urgent need for comprehensive policy reforms that prioritize inclusivity and equitable access to housing for all residents. Such reforms should focus on enhancing transparency and participation in the governance processes, ensuring that all community members, particularly marginalized groups, have a voice in shaping their urban environments [10]. This inclusive approach not only addresses the immediate needs of vulnerable populations but also fosters resilience within communities, ultimately contributing to a more sustainable urban future. This necessitates a re-evaluation of existing policies to align them with the principles of multilevel governance, ensuring that diverse community voices are heard and integrated into urban planning processes [14,15,16].

Despite these challenges, few academic works have proposed a structured typology of the “exceptional cases”, those AUGIs that remain outside the reach of the legal framework despite efforts to normalize them. The concept of “double marginality”, explored in recent exploratory work [12], addresses this gap by combining historical informality with present-day legal and procedural exclusion. However, this concept has yet to be fully systematized and operationalized in the context of Portuguese urban planning law. This gap in the literature highlights the need for further research to develop a comprehensive typology that can inform policy interventions and promote effective governance in addressing informal urbanization in Portugal. This typology should consider the unique characteristics of each AUGI, emphasizing the need for localized solutions that address specific community contexts and challenges. Developing such a typology is essential for ensuring that policy measures are tailored to the diverse realities of informal settlements, facilitating more effective governance and integration of these areas into the urban fabric.

Despite the legal and urban relevance of AUGIs in Portugal, academic research on the subject remains limited and often fragmented. Most existing studies are framed within urban planning or housing policy discourses, with few offering integrated legal and territorial analyses. Some authors have focused on the historical origins of informal settlements and the evolution of urban sprawl in Lisbon’s metropolitan periphery [17,18], while others have explored the procedural and governance challenges faced by municipalities in applying Law No. 91/95 and its successors [12]. However, there is still a lack of typological approaches that account for cases of persistent exclusion, especially those that fall outside the regularization path due to non-compliance with cumulative legal conditions.

Urban informality is not only a planning issue but also a question of urban citizenship, the recognition of inhabitants as legitimate subjects of rights within the city. As [19] and later [20] emphasized, the “right to the city” includes access to infrastructure, participation in urban governance, and security of tenure. In the Portuguese context, doubly marginal AUGIs highlight the tension between formal legal frameworks and lived urban realities, where residents often experience long-term integration into city life while remaining legally excluded. This condition creates what [21] terms “insurgent citizenship”, a demand for recognition beyond property-based rights, particularly among marginalized populations. The persistence of legal invisibility, even in spatially consolidated settlements, reveals the inadequacy of a strictly normative and procedural approach to urban regularization.

The decentralization of urban policy implementation in Portugal has accentuated territorial inequalities. While Law No. 70/2015 assumes a homogeneous capacity across municipalities to lead reconversion processes, the reality is that institutional, technical, and financial disparities significantly influence outcomes. Smaller municipalities or those with weaker planning departments struggle to meet the administrative and procedural requirements imposed by law. Moreover, political priorities and interpretations vary, creating uneven treatment for similar AUGIs across municipal borders. This disparity reinforces a “postcode injustice”, whereby access to legal recognition is shaped not by residents’ actions, but by the institutional characteristics of the municipality in which their AUGI is located [11]. Such conditions challenge the principle of territorial cohesion embedded in Portuguese planning law and underscore the need for coordinated equity-driven responses at the national level.

2.3. Legal Framework and Territorial Justice in Portugal

In the context of urban informality, public policies play a central role not only in enabling regularization but also in producing or perpetuating spatial inequalities.

Contemporary urban theory, based on the concept of the right to the city, argues that access to urban space should be considered a collective right that transcends market logic and property-based rights [19,20]). This principle intersects with the notion of territorial justice, which calls for an equitable distribution of urban resources, infrastructure, and opportunities across different geographic and socio-economic groups [22].

In Portugal, although the creation of the AUGI regime under Law No. 91/1995 was an innovative step towards the recognition and integration of informal settlements, it also incorporated a logic of self-responsibility. Residents were expected to organize into administrative commissions, bear the financial costs of regularization, and navigate complex bureaucratic and technical processes. This model, carried forward in Law No. 70/2015, places a heavy burden on residents, disproportionately affecting older populations, low-income households, and those with limited legal or technical knowledge, thereby exacerbating spatial and social inequalities.

A critical reading of Law No. 70/2015 reveals both its scope and limitations in terms of promoting territorial justice and fulfilling the right to the city:

• Article 1.º (Object and Scope) defines AUGIs narrowly as areas parcelled without a license prior to December 1984, and only if classified as urban or urban expansion land in municipal land-use plans. This legal framing excludes more recent informal settlements or those outside designated zones, despite their socio-urban relevance.
• Article 3.º (Duty to Regularise) places responsibility for reconversion directly on owners and occupants, including the financial burden of infrastructure and legal procedures. This can be particularly punitive or at least limiting for residents who acquired properties without being fully aware of their informal status or who lack the means to participate effectively (not forgetting that these owners should not be favoured over others who have always acted within the law). Criticism of this situation is very delicate, as it raises the question of benefiting the offender and/or rewarding the offence.
• Article 5.º provides a mechanism for regularizing areas only partially classified as urban/urban expansion, but under strict cumulative conditions. This provision has been interpreted restrictively by some municipalities, limiting its applicability and reinforcing legal fragmentation between territories.
• Article 46.º introduces a discretionary mechanism through which municipalities may exceptionally authorize the maintenance of constructions that fail to meet legal criteria. However, it requires municipal regulation and political will, which are often lacking or uneven across regions.
• Article 48.º addresses areas that cannot be regularised, where buildings may have to be demolished and residents rehoused. Although this article describes a process of social survey and rehousing (e.g., through social housing mechanisms), it implies the withdrawal, supported by legal justifications linked mainly to environmental issues but not only, of the urban rights of entire communities, contrary to the principles of inclusion and the right to remain.
• Article 56.º A mandates municipalities to report reconversion processes to the central administration. However, this focuses on data collection rather than support or intervention, illustrating the state’s monitoring but not redistributive role in addressing spatial injustice.

These legal mechanisms, though designed to manage urban irregularities, fail to account for the structural conditions that gave rise to informal development, and often treat residents as obstacles rather than stakeholders in urban governance. Furthermore, the heavy reliance on local governments, with uneven technical and financial capacities, creates significant disparities in implementation.

The Portuguese planning system has long relied on exception-based legal instruments to address complex or politically sensitive urban issues. As [22] argues, this has led to the “normalization of the exceptional,” whereby transitory regimes, such as those regulating AUGIs, become permanent fixtures in urban governance, rather than catalysts for systemic reform. Instead of establishing clear and inclusive legal norms, the planning system often resorts to temporary frameworks that manage informality without resolving its root causes. This creates zones of suspended legality, where territorial rights and obligations remain unclear, reinforcing legal uncertainty and spatial inequality. Such dynamics provide a critical backdrop to the concept of “double marginality” developed in this article, which seeks to unpack the long-term effects of legal exclusion on informal urban areas.

Recent Portuguese legal literature has increasingly focused on the notion of territorial justice, emphasising the need for consistency, proportionality and equity in the application of planning law. Authors such as [23] have highlighted how exceptional regimes in Portuguese urban planning, including those governing AUGIs, tend to institutionalise unequal treatment between municipalities, as they are based on administrative capacities that are far from uniform. Similarly, ref. [9] argue that inconsistencies in planning and land use regulation can exacerbate spatial inequalities by allowing legal obligations, environmental restrictions, and procedural requirements to operate unevenly across territories. The structural tension between environmental protection, urban regularisation and constitutional guarantees of territorial cohesion is explicit, reinforcing the idea that the challenges faced by doubly marginalised AUGIs are not only urbanistic but are fundamentally rooted in the legal architecture.

2.4. Legal Silence and Institutional Ambiguity

Building on this, several works have highlighted the ambiguities and omissions of the current legal framework, particularly regarding territories that fall outside formal eligibility for regularization. Ref. [24] points to the lack of procedural alternatives or compensation mechanisms for residents living in areas designated as “insusceptible of regularization” under Article 48 of Law No. 91/1995. These cases illustrate how legal exclusion operates not only through prohibition but also through the absence of administrative action, a passive marginalization that sustains illegality over time. The literature on planning and informal settlements increasingly recognizes this form of legal inertia as a mechanism of structural inequality, where law’s silence effectively produces exclusion [2,24,25,26,27].

While urban regularization is often treated as a technical planning issue, recent work has emphasized the need to integrate it with broader housing policy frameworks. A study focused on the municipalities of Loures and Odivelas demonstrates that the legal tools for AUGI regularization (Law No. 70/2015) and the public housing programs under the 1.º Direito framework, a national program launched in 2018 to support municipalities in addressing situations of severe housing deprivation through subsidized access to adequate housing, have evolved in parallel but largely disconnected ways. As a result, many families living in informal settlements find themselves ineligible for either program, excluded from reconversion due to environmental or procedural barriers, and simultaneously unable to access public housing subsidies due to land status or documentation gaps [27]. The lack of coordination between land regularization and housing rights reinforces territorial inequality, and risks institutionalizing informality for communities that cannot meet rigid legal or technical criteria.

In this sense, the current regime struggles to align with the normative goals of urban justice, producing a legal geography in which the right to the city is unevenly distributed. Residents of certain AUGI benefit from proactive municipalities and cooperative neighbours, while others, often more precarious, face indefinite exclusion.

3. Methodology

This study adopts a mixed and interdisciplinary methodology, combining legal analysis, case study research, and spatial cartography. These three dimensions were not considered independently but integrated through a comparative protocol applied across all five case studies. For each location, data were collected from municipal and legal documents, planning instruments, and spatial information systems, supplemented by field visits. The analysis followed a three-step process: (1) identification of key constraints (social, legal, environmental); (2) classification of each case according to these dimensions; and (3) cross-comparison to identify recurring patterns of exclusion and structural bottlenecks.

The results were then synthesised into a typology that captures the nature of “double marginalisation” across multiple layers of vulnerability. This qualitative approach allows for a structured yet flexible understanding of the institutional and spatial dynamics at play. The goal is to explore the institutional, legal, social, and environmental barriers that continue to exclude certain AUGIs from the urban regularisation framework, despite the existence of legal instruments.

(a)

Document Analysis. A critical legal and policy review was conducted, focusing on: i. National legislation, particularly Law No. 91/95 and its consolidated version in Law No. 70/2015, as well as complementary frameworks such as the Legal Regime of Urbanisation and Edification (RJUE) and RJIGT (Legal Framework for Territorial Management Instruments); ii. Municipal regulations, urban planning instruments, and minutes of local authorities in municipalities with high concentrations of AUGIs, specifically Odivelas, Loures, Sintra, Seixal, and Amadora (all within the LMA); iii. The training and coordination strategy of the Directorate-General for the Territory (DGT) under Article 56-B of Law 70/2015, analysed as an institutional response to legal fragmentation and uneven implementation at the local level.

This legal and documentary corpus provided the foundation for identifying gaps between legal frameworks and real-world applications.

(b)

Case Studies. Five case studies were selected to represent diverse expressions of “double marginality”, areas that are both historically informal and currently excluded from regularisation due to procedural, legal, or spatial constraints. The selected areas are: i. Bairro da Serra da Luz (Odivelas); ii. Bairro da Ribeirada de São José (Odivelas); iii. Bairro da Torre dos Trotes (Loures); iv. Bairro da Tabaqueira (Sintra); v. Marco do Grilo (Seixal).

These areas were chosen using purposive sampling based on the following criteria: i. Geographic and institutional diversity, reflecting different municipal strategies; ii. Degrees of risk, including geotechnical hazards, legal irregularities, and social vulnerability; iii. Presence or absence of formal governance structures, such as joint administrative commissions required by law.

Field visits and secondary data collection enabled detailed profiling of each site, considering both legal status and lived realities.

(c)

Spatial and Cartographic Analysis. To complement legal and qualitative insights, a spatial analysis was carried out using: i. Data from the SIAUGI platform (AUGI Information System from DGT), which maps formally recognised AUGI across the national territory; ii. Satellite imagery and orthophotos (via Google Earth and municipal GIS platforms), used to identify spatial characteristics, infrastructure deficits, and surrounding land use; iii. Mapping of AIRU (Areas Insusceptible to Urban Regularisation) and their overlap with vulnerable populations, revealing territorial inequalities embedded in the legal framework.

This spatial dimension helped to visualise patterns of exclusion and informed the typology proposed later in the article.

Although qualitative in nature, the analytical protocol adopted in this study is transparent and transferable, allowing for replication in other contexts with similar legal and territorial characteristics.

This investigation did not involve semi-structured interviews or surveys. Instead, it used a structured observation protocol to document physical conditions, infrastructure degradation, informal service provision, and indicators of collective organisation. The methodology relied on photographs, occupation patterns, building conditions, and community governance structures. Social vulnerability and low mobilisation were assessed using observable proxies, such as use of public space, housing conditions, and levels of activity of residents’ committees. These indicators were confirmed in secondary sources, including planning instruments, technical reports, and municipal data, ensuring a consistent and empirically valid assessment.

However, it is important to note that reliance on secondary data introduces some methodological constraints. Municipal planning documents, regulatory instruments, and institutional reports vary significantly in quality, completeness, and analytical depth, reflecting uneven technical capacities and policy priorities among municipalities. These sources may also incorporate institutional biases, particularly in the classification of informal areas, communication of implementation progress, and interpretation of legal restrictions. Such limitations do not compromise the comparative value of the study, but they do require a cautious and context-sensitive reading of the material, which was taken into account in the analytical protocols adopted.

4. Results

Fieldwork and multidimensional analysis identified a persistent group of AUGIs excluded from the regularisation process in LMA (Figure 1). The five cases studied—Serra da Luz (Figure 2, Figure 3 and Figure 4), São José (Figure 5, Figure 6 and Figure 7), Torre dos Trotes (Figure 8, Figure 9 and Figure 10), Tabaqueira (Figure 11, Figure 12 and Figure 13) and Marco do Grilo (Figure 14, Figure 15 and Figure 16)—reveal what this study refers to as ‘double marginality’, a condition characterized by both a historically irregular origin and a present-day legal and procedural exclusion.

To better understand this condition, a three-dimensional typology is proposed, categorizing exceptional cases based on social–demographic, legal–political, and environmental–risk variables.

4.1. Social and Demographic Dimension

Several AUGIs are home to aging populations, low-income residents, and socially vulnerable households. In many cases, the collective administrative structures required by Law No. 70/2015, such as joint owners’ commissions, are either inactive or absent, largely due to:

• Advanced age of residents, leading to low participation in formal procedures;
• Economic vulnerability, limiting the ability to co-finance infrastructure works;
• Lack of social mobilization, as many residents are either disillusioned or unaware of their legal options.

These social factors act as de facto barriers to the implementation of the regularization process, even when legal avenues exist.

4.2. Legal and Political Dimension

Several obstacles relate to the legal configuration of the land and the governance model required for reconversion:

• Unclear or disputed land ownership (e.g., occupied military or other public lands);
• Areas not formally classified as urban/urban expansion in PDMs which excludes them from Article 1 and Article 5 eligibility under Law No. 70/2015;
• Lack of municipal political will or absence of enabling regulation (e.g., Art. 46’s exceptional authorization mechanisms not implemented);
• Missing or dysfunctional administrative commissions, which are essential for initiating and managing the reconversion process under Article 15.

The Tabaqueira neighbourhood in Sintra is characterised by informal housing developments for residential and semi-industrial use. Despite the existence of some infrastructure, the neighbourhood is located close to protected forest areas, which causes environmental conflicts. The absence of an active administrative committee has hampered progress in regularisation, even where there is formal eligibility.

The São José neighbourhood in Odivelas has an ageing population with low social mobilisation, aggravated by informal forms of collective ownership that complicate legal formalisation. Although it does not present significant environmental risks, the absence of an administrative committee and legal fragmentation have brought the reconversion process to a virtual standstill.

In some municipalities, similar AUGIs receive different treatment due to diverging interpretations of eligibility, creating perceptions of legal inequality and territorial injustice.

4.3. Environmental and Risk Dimension

Several AUGIs are located in areas with significant physical or technological risk, including:

• Slope instability and landslide-prone terrain (e.g., hillside settlements in Loures and Odivelas);
• Flood-prone zones (e.g., Serra da Luz);
• Infrastructure easements, such as aeronautical or telecommunication protection zones, which legally restrict construction and regularization.

These risks often serve as legal grounds for exclusion, particularly under Article 48 of the law, which designates such areas as insusceptible of regularization. Even when informal dwellings have existed for decades, their environmental context effectively places them in a legal dead end.

4.4. Proposed Typology: Cross-Analysis of Variables

There is a distinction between legal ineligibility and procedural exclusion, highlighting their different mechanisms and the type of marginalisation that results from them. Legal ineligibility concerns settlements that do not meet the criteria established by Law No. 70/2015, making regularisation impossible, regardless of local efforts. On the other hand, procedural exclusion arises when regularisation is legally feasible but prevented by institutional limitations, inactive commissions, ambiguous ownership, or municipal hesitation to employ exceptional measures. This distinction was systematically applied in the five case studies, ensuring that the proposed typology considers both the normative limits of the legal framework and the operational shortcomings that explain de facto exclusion.

The following

Table 1. Key variables characterisation across the studied AUGI cases.

Case	Social Vulnerability	Legal Irregularity	Environmental Risk	Admin. Commission	Legal Eligibility	Regularization Status
Serra da Luz (Odivelas)	High (elderly)	Property of the Ministry of Finance	Landslide zone Flood-prone zone	Partial	Partial (Art. 5)	Stalled
Bairro da Tabaqueira (Sintra)	Medium	Informal land titles, mixed use	Proximity to protected forest area	Inactive	Yes	Partial
Bairro da Torre dos Trotes (Loures)	High	Informal land titles	Moderate geotechnical risk	Active	Yes	Partial progress
Bairro de São José (Odivelas)	High	Uncertain collective ownership	No relevant risks	Absent	No (Art. 5)	Excluded
Marco do Grilo (Seixal)	Low	Mixed ownership	Proximity to infrastructure easements	Active	Partial	Delayed

synthesizes the key variables across the studied AUGI cases, offering a typological matrix that reflects their exclusion patterns and potential routes (or blockages) to regularization:

The typology presented in Table 1 is the outcome of this comparative analysis. Each variable reflects criteria identified through both documentary analysis and field observation. While this is not a statistical representation, the structured comparison allows for the identification of patterns and typological clusters. The aim is not to generalize, but to highlight recurring conditions that may inform differentiated legal and policy responses.

The combined analysis of the five cases shows that double marginality emerges not from isolated deficits but from the cumulative interaction of social vulnerability, legal irregularity and environmental constraints. These dimensions reinforce one another: weak social organisation limits the capacity to navigate legal procedures; legal ambiguity amplifies the consequences of institutional inertia; and environmental risks trigger exclusionary interpretations of planning law. When these vulnerabilities overlap, they generate a self-perpetuating condition in which settlements remain structurally outside the formal urban system, regardless of their consolidation or duration. This cumulative effect demonstrates that double marginality is not exceptional but systemic, shaped by the way the legal framework and governance practices intersect with uneven territorial conditions.

4.5. Institutional Perspectives on Legal and Procedural Impasses

While field data and spatial analysis helped construct the typology of doubly marginal informal areas, institutional voices added critical depth to understanding why these cases persist. Interviews with municipal technicians revealed a widespread perception of legal paralysis, particularly regarding areas classified under Article 48 of Law No. 70/2015 as insusceptible to regularization.

A revealing comment came from a senior official in Lisbon’s urban planning department, who acknowledged that: “There are neighborhoods that everyone knows cannot be regularized, but we also don’t know what to do with them.” [27]. This quote illustrates an underlying institutional deadlock: municipalities are aware of the legal limitations but lack policy alternatives. In practice, this often leads to a strategy of informal toleration or “freezing” of these territories, which are neither regularized nor removed from the urban system. The absence of political guidance, interdepartmental coordination, or dedicated relocation resources reinforces this stasis.

Such accounts underscore the need for a governance model that moves beyond the binary of legality vs. illegality and instead addresses informality as a durable urban condition that requires proactive and inclusive responses.

5. Discussion

The analysis of the five selected AUGIs in the Lisbon Metropolitan Area reveals consistent patterns of exclusion in different municipalities. These results support the conceptual framework of ‘double marginality’, demonstrating how overlapping vulnerabilities, legal ambiguity, institutional inertia and environmental constraints work in practice. In this section, we reflect on these findings to assess the adequacy of the existing legal framework and discuss its implications for urban policy and planning in Portugal.

Although the law introduced regularisation mechanisms and sought to empower municipalities, it proved inflexible and exclusionary for a significant portion of the urban areas most in need of intervention.

5.1. Legal Inflexibility and Social Invisibility

Law No. 70/2015 frames the regularization process around a standardized legal model, one that assumes clear property ownership, active community governance, and financial capacity. However, many of the excluded AUGIs present the opposite conditions as ambiguous land titles, aging or economically precarious populations, and environmental constraints that defy easy legal categorization.

The cumulative requirements set out in Articles 1 and 5 narrow the legal eligibility of settlements, particularly those partially classified as non-urban or located in sensitive areas. Moreover, Articles 46 and 48, which allow for exceptional authorizations or mandatory demolition with relocation, are inconsistently applied and rarely supported by concrete implementation tools or financial resources.

These rigid provisions do not account for the historical consolidation and lived urbanity of many of these areas. As such, the law effectively renders certain resident’s invisible, excluding them from the right to formal urban citizenship despite decades of physical and social integration into the city.

5.2. Municipal Disparities and Legal Fragmentation

The implementation of the AUGI regime is highly decentralized, relying on the discretion and capacity of local authorities. This has produced a patchwork of interpretations, where similar settlements are treated differently depending on local planning culture, technical expertise, and political will. In many cases, complex and fragmented regulations, combined with a shortage of technical and human resources, make law enforcement costly, reinforcing exclusion through administrative inertia.

Some municipalities, such as Seixal or Odivelas, have invested in proactive engagement, while others have shown inaction, either due to limited resources or political resistance to assuming responsibility for informal settlements. The absence of clear national coordination and enforcement mechanisms leads to territorial injustice, where residents in similar conditions face different futures based on administrative boundaries.

Additionally, many municipalities have not implemented the exceptional tools provided by law, such as the creation of relocation programs or the approval of regulatory exceptions under Article 46. As a result, some AUGIs remain legally stagnant even when viable technical solutions exist.

5.3. Spatial Justice and Unequal Citizenship

This situation reinforces a broader dynamic of unequal urban citizenship, where access to the legal city is mediated by property, governance structures, and geography. The inability of some residents to regularize their homes is not merely a technical failure, it also reflects a deeper mismatch between the universal ideals of planning law and the particularities of lived urban experience.

Perceptions of injustice are especially acute in cases where neighbouring AUGIs are regularized while others are excluded due to narrow interpretations of zoning plans or risk maps. This undermines trust in institutions and weakens public participation, especially in socioeconomically fragile communities.

5.4. Legal Silence and the Perpetuation of Informality

The long-term persistence of AUGIs that remains outside formal urban integration is both a symptom and a cause of broader territorial dysfunction, particularly in metropolitan areas where these settlements are most concentrated. A key focus of this article is precisely on the structural causes behind this persistence, especially in the case of areas deemed legally “insusceptible to regularization” as defined in Article 48 of Law No. 70/2015. These areas are often excluded from the regularization process due to environmental constraints or physical risk conditions, such as floodplains, geotechnical instability, or ecological protection zones.

As seen in Serra da Luz and Marco do Grilo, residents remain in a prolonged state of legal and spatial limbo due to flood-prone or infrastructure-restricted zoning, with no compensatory mechanisms currently activated under Article 48. This vacuum contributes to the historical perpetuation of informality, with far-reaching consequences. Residents continue to live in precarious conditions, often in areas environmentally sensitive or unsafe, without proper infrastructure, legal security, or protection from eviction. Simultaneously, a parallel housing market persists, where informal dwellings are rented or sold without oversight, reinforcing spatial inequality.

This dynamic is further intensified by demographic change, particularly the aging of residents, which limits collective capacity to engage in bureaucratic processes or advocate for change. As a result, the legal and institutional silence surrounding these doubly informal AUGIs has become a self-reinforcing mechanism of exclusion, undermining efforts toward spatial justice and sustainable urban governance.

The typology proposed in this article offers a structured and empirically grounded framework that not only classifies exceptional cases of informal spaces but also serves as a tool for diagnosing regulatory incompatibilities and institutional deadlocks. By delineating cases along sociodemographic, legal-political, and environmental risk dimensions, it provides a replicable methodology for identifying where and why current legal frameworks are insufficient. In theoretical terms, this typology contributes to ongoing debates on spatial justice [22,26]) and the right to the city, highlighting how legal exclusion is often the result of cumulative vulnerabilities rather than isolated legal violations. In practice, the typology can support specific reforms of Law No. 70/2015, particularly with regard to the need for differentiated legal treatment for neighbourhoods currently considered unsuitable for regularisation. It can also serve as a diagnostic tool for municipalities to prioritise interventions, mobilise resources, and negotiate exceptions or alternative compliance mechanisms in a transparent and criteria-based manner.

Furthermore, this framework can support the design of new planning and housing policies, helping to clarify the intersection between legal invisibility and socio-environmental vulnerability. As such, it encourages a shift from a procedural model to a contextual model of regularisation, which aligns with international trends in adaptive urban governance [14,15]. By moving beyond case-by-case exceptionality towards a typological approach, the study increases the capacity of urban planners and policymakers to respond systematically to complex scenarios of informality.

5.5. Fragmented Governance and Missed Policy Integration

An additional layer of marginalization emerges from the disconnect between urban regularization policies and housing policy instruments. As highlighted in recent municipal-level research, the lack of coordination between Law No. 70/2015 and national housing programs, particularly the 1.º Direito strategy, leaves many residents of informal settlements without access to either legal recognition or adequate housing support [27]. In practice, families living in areas considered insusceptible to regularization (e.g., under Article 48) are often ineligible for public housing aid, either due to land status issues, unclear tenure, or procedural bottlenecks.

This results in a policy vacuum, where two parallel systems, one focused on land regularization and the other on housing, operate without intersection, despite serving overlapping populations. The consequences are especially severe for vulnerable groups, who are excluded from both the formal housing market and the legal urban grid. Without a strategic articulation between planning and housing, informal settlements risk becoming permanently invisible to both systems, reinforcing territorial injustice and undermining the social goals of both legal frameworks.

5.6. International Comparison and Missed Opportunities

Brazil and Spain were selected for comparison due to the historical prevalence of informal areas, their legal trajectories rooted in civil law traditions, and their relevance in the contexts of Iberian and Lusophone urban policies.

The comparative analysis between Portugal, Brazil, and Spain offers relevant perspectives due to common patterns of urban informality and post-authoritarian planning systems, albeit with different urban types and forms, legal instruments, and institutional capacities.

Brazil, under the Estatuto da Cidade (City Statute), implements the principle of the social function of property through flexible tools such as special urban adverse possession and special zones of social interest (ZEIS), which facilitate the regularisation of ownership and the provision of infrastructure, even in ecologically sensitive areas, provided that certain consolidation and vulnerability limits are met [28].

A more detailed look at Southern European experiences helps clarify the institutional distance between Portugal and its closest comparators. In Spain, several autonomous communities have used Special Regularisation Plans (Planes Especiales de Regularización) to retroactively incorporate informal settlements into the planning system, relying on exceptional zoning adjustments, simplified administrative steps, and crucially, regional financial co-responsibility that reduces the burden placed on residents and municipalities. Italy follows a different but equally illustrative trajectory through repeated condoni edilizi, urban amnesties that legalise non-compliant constructions upon meeting technical safety requirements and paying compensatory fees, supported by highly centralised procedures designed to accelerate processing and reduce municipal discretion. These mechanisms, though contested, reveal operational features largely absent from the Portuguese model: procedural flexibility, financial redistribution beyond the local level, and institutional coordination capable of absorbing heterogeneity rather than amplifying it.

In contrast, the Portuguese framework remains legally rigid and procedural, with few compensatory mechanisms or margins for interpretation at the local level, particularly for areas considered unsuitable for conversion under Article 48. This reveals a gap not only in legal instruments, but also in national coordination and redistributive policy. The choice of Brazil and Spain for comparison is based on their socio-historical trajectories of informal urbanisation and the use of innovative legal and political instruments that could serve as a basis for future reforms in Portugal. Both cases show how adaptable and equity-oriented instruments can balance legal integration with environmental and urban planning objectives, providing alternative avenues that Portugal has not yet institutionalised.

5.7. Limitations of the Research and Avenues for Future Development

This study has some limitations that should be acknowledged. The analysis is based on a small number of case studies in the Lisbon Metropolitan Area, which, although adequate for exploring exceptional situations and deepening the notion of double marginality, does not allow for statistical generalisations or an exhaustive characterisation of the phenomenon in the national territory. The availability of institutional information also proved to be uneven across municipalities, limiting the comparability of the situations observed and highlighting the very administrative fragmentation that the study seeks to address. Data on the implementation of the mechanisms provided for in Law No. 70/2015 remain incomplete, inaccessible or unsystematic, limiting the longitudinal assessment of the regime’s effectiveness. Furthermore, the lack of national indicators on excluded AUGIs prevents the construction of metrics on the prevalence and intensity of legal marginalisation.

However, these limitations also open up several avenues for future research. Studies that integrate quantitative methodologies could map the territorial distribution of doubly marginalised AUGIs and identify patterns of inequality between municipalities. Comparative research in other regions of the country would allow us to assess the extent to which the dynamics identified in the LMA are replicated in contexts with different institutional capacities. A more systematic interdisciplinary approach, linking urban planning, administrative law, housing policies and social geography, could contribute to social and environmental risk assessment models applicable to contexts of consolidated informality. Finally, international comparative assessments, especially with countries that have developed more flexible regularisation instruments, can offer useful contributions to a review of the Portuguese legal framework and to the construction of more tailored and agile responses to territories that remain in a condition of legal invisibility and accumulated vulnerability.

6. Conclusions and Recommendations

6.1. General Remarks

This article has explored the structural barriers that prevent certain Informally Originated Urban Areas (AUGIs) in Portugal from completing or even initiating their regularization processes. Through an interdisciplinary and empirical approach, we identified a subset of cases marked by “double marginality”, settlements that are both historically marginal and legally excluded from the current framework established by Law No. 70/2015.

The typology developed in this study demonstrates that exclusion arises not from a single factor, but from the overlap of legal, social, and environmental vulnerabilities. These include ambiguous land tenure, lack of formal governance structures, limited resident capacity, and the presence of environmental risks. In many cases, the very populations who would benefit most from legal integration are those least equipped to navigate the system.

At the same time, the law places the burden of regularization primarily on residents and municipalities, without sufficient national coordination or institutional and financial support, resulting in uneven outcomes across the territory. As a result, spatial and legal fragmentation persists, undermining principles of territorial justice and the right to the city.

6.2. Policy and Legal Recommendations

All our previous research and corresponding reflections should also be linked to experiences in Spain and Brazil that offer concrete legal insights that could inform a future reform of the Portuguese framework. The Spanish model demonstrates how exceptional planning instruments supported at the regional level can limit the disproportionate burden placed on municipalities, while the Brazilian regime shows the value of legally recognised presumptions of consolidated occupation and strong central coordination to overcome procedural deadlock. Incorporating elements such as regional co-responsibility, presumptive legal recognition in long-standing settlements and simplified exceptional procedures would strengthen the Portuguese system’s capacity to address structurally excluded AUGIs and reduce the legal inertia that sustains double marginality.

To overcome these shortcomings and ensure more inclusive urban governance, we propose several policy guidelines.

6.2.1. Create a Dedicated Legal Framework for “Doubly Marginal” Areas

A new legal regime or sub-regime should be established to address AUGIs that are currently excluded from Law No. 70/2015 due to:

• Unclear urban classification;
• Lack of administrative commissions;
• Environmental or technical constraints.

This regime should allow for simplified procedures, contextual exceptions, effective solutions for the populations living in environmental risk areas and alternative compliance paths, including the recognition of long-standing occupation and urban consolidation.

This legal framework should not automatically authorise the regularisation of territories located in environmentally sensitive or high-risk areas. Instead, it should offer structured and transparent solutions, including risk mitigation measures, selective rehousing or specific legal treatment, based on multidisciplinary assessments. These assessments should include technical studies on environmental risks, urban compatibility and social diagnostics to ensure that any intervention or decision respects both territorial justice and environmental safety.

6.2.2. Establish Decentralized Technical and Financial Support Mechanisms

The current model assumes that residents and municipalities possess the capacity and resources to manage reconversion processes. This is not the case in many of the most vulnerable areas. Therefore, we recommend the creation of:

• Multidisciplinary technical support teams, coordinated at the regional level (e.g., by Regional Coordination and Development Commissions (CCDR) or General Directorate of Territory (DGT));
• Targeted funding programs for infrastructure development and community engagement;
• Legal aid and mediation services to assist residents with title clarification and collective action formation.

These support structures would help equalize access to regularization, particularly in socioeconomically disadvantaged contexts.

6.2.3. Improve Coordination Between Planning Instruments and Relocation Policies

For areas classified as “insusceptible to regularization” under Article 48, the law foresees demolition and rehousing, but implementation remains weak and fragmented.

To make this process more equitable and effective, we believe that is essential to:

• Strengthen the link between planning instruments and rehousing programs (such as the Municipal Housing Charter);
• Ensure that all relocation is preceded by social diagnostics and supported by realistic housing alternatives, preferably within the same municipality;
• Use existing public housing stock or allocate public land for construction under affordable regimes.

6.2.4. Operational Recommendations Tailored to Exclusion Types

Building on the typology developed in Section 4.4, this research proposes differentiated policy responses that address the distinct barriers faced by various types of “doubly marginal” AUGIs. These recommendations are operationalized according to three main dimensions:

(a)

Legal and Institutional Obstacles (e.g., São José, Tabaqueira)

• Immediate action: Create a fast-track mechanism for legal clarification of land tenure, supported by regional legal aid offices.
• Medium-term: Mandate the creation of administrative commissions through municipal facilitation, particularly in aging communities with low mobilization.
• Long-term: Introduce legal presumptions of occupancy for settlements with over 30 years of consolidation, akin to adverse possession mechanisms used in Brazil.

(b)

Environmental and Risk-Based Constraints (e.g., Serra da Luz, Marco do Grilo)

• Immediate: Conduct independent environmental audits to assess real risk and allow for proportional regularization where feasible.
• Medium-term: Develop municipal “risk mitigation plans” integrated with housing relocation strategies (e.g., through 1.º Direito or similar programs).
• Long-term: Modify Article 48 to include case-by-case exceptions when social costs of relocation outweigh environmental risks.

(c)

Governance and Implementation Gaps (e.g., Torre dos Trotes)

• Immediate: Deploy regional technical taskforces (e.g., via CCDR) to unblock stalled processes.
• Medium-term: Establish state-funded municipal co-financing programs for infrastructure upgrades in eligible AUGIs.
• Long-term: Institutionalize a national observatory on AUGIs to track progress, standardize interpretations of the law, and issue annual reports on territorial equity.

The implementation of these guidelines faces substantial obstacles, despite addressing structural limitations. Establishing a legal framework for these marginal territories requires political will and technical capacity, which are not universally present among local authorities. Creating regional/metropolitan technical teams and raising funding requires budgetary adjustments and inter-institutional cooperation, which has historically been weak in Portugal. Coordination between planning instruments and rehousing policies requires significant reforms within local authorities with limited resources. Obviously, greater permissiveness in environmentally vulnerable areas faces legal and institutional opposition due to concerns about future liabilities and conflicts with environmental protections. While these challenges do not diminish the importance of the proposals, they highlight the need for broader reforms in territorial governance, including strengthening municipal capacities and competences, ensuring stable funding, and promoting better coordination between the planning, housing, and environment sectors.

6.3. Final Remarks

These recommendations aim to bridge the gap between general policy intent and local implementation, ensuring that legal, social, and environmental complexities are addressed through tailored and viable approaches. Rather than proposing technical solutions, they advocate for a strategic shift in how informal territories, particularly those marked by double marginality, are addressed in legal and planning systems. By recognising the structural and cumulative nature of exclusion, the proposals call for regulatory mechanisms that are socially sensitive and spatially just. The notion of double marginality also has theoretical implications for debates on informal urbanism. While concepts such as Holston’s insurgent citizenship emphasise bottom-up demands for recognition and Yiftachel’s grey spaces highlight zones of legal ambiguity tolerated by the state, these Portuguese cases show a different dynamic as they constitute long-standing settlements that are simultaneously consolidated, institutionally recognised as a problem, and yet structurally excluded through a combination of legal rigidity and procedural fragmentation. Double marginality thus broadens these frameworks, demonstrating how legal exclusion can persist not only through informality, but also through the cumulative interaction of bureaucratic design, unequal municipal capacity, and risk-based constraints. This contributes to a more systemic understanding of how certain populations remain trapped in a condition of permanent legal liminality, even in consolidated European urban contexts, where insurgent practices or discretionary tolerance only partially explain the persistence of informality.

In addition to responding to the limitations of Law No. 70/2015, this article contributes to broader reflections on the normative design of spatial planning systems. Clarifying the legal and institutional characteristics that prevent or enable effective implementation, such as procedural flexibility, eligibility limits and multilevel coordination, is essential not only to resolve informal urban situations, but also to promote regulatory innovation and operational effectiveness in urban and territorial governance.