Introduction

The preceding parts of this series have examined the substantive and procedural protections afforded by the Convention against expulsion: the absolute prohibition of refoulement under Article 3 (Part I); the protection of private and family life under Article 8 (Part II); the procedural safeguards under Articles 5, 13, and — where applicable — 6 (Part III); and the specific procedural regime for lawfully resident aliens under Article 1 of Protocol No. 7 (Part IV).

Although the Court has developed distinct standards in each of these areas, the applicability and ultimate operation of these standards frequently turn on the principle of proportionality. Particularly in the context of Article 8 ECHR — where the permissibility of expulsion is assessed against the interference with private and family life — the Court’s central question is whether the interference pursued a legitimate aim, responded to a pressing social need, and was ultimately proportionate in the circumstances of the case.

Expulsion proceedings are paradigmatic cases in which the State’s interest in maintaining public order or implementing its immigration policy must be balanced against the individual’s rights to family life, social integration, and personal integrity. To ensure the consistency and integrity of this balancing exercise, the Court has developed over time a standardised proportionality test, which concretises the factors to be weighed and serves as an objective yardstick for the necessity of the interference.

1. The Foundations: Boultif and Üner

The Court first articulated the criteria governing the proportionality assessment in Boultif v Switzerland,¹ a decision examined in Part II. Those criteria were systematised and expanded in Üner v Netherlands,² where the Grand Chamber established the standard test for striking a fair balance between the individual’s interests and the public interest pursued by the State.

Together, the Boultif–Üner line of authority provides a coherent methodological framework that continues to shape the Court’s expulsion jurisprudence across the Convention’s protective provisions.

2. The Principal Criteria

In applying the proportionality test, the Court takes into account, inter alia, the following factors:

1. The nature and gravity of the offence committed by the applicant giving rise to the expulsion decision.
2. The length of time elapsed between the offence and the expulsion decision, and the applicant’s conduct during that period.
3. The duration of the applicant’s stay in the Contracting State, with particular attention to whether settlement occurred during childhood.
4. The nature of the applicant’s family situation, including the length of the marriage, the nationality of the spouse, and whether the couple live together.
5. The age and custody arrangements of the applicant’s children, and considerations relating to the best interests of the child.
6. The feasibility of family members relocating to the destination country, and the impact of displacement on the family unit.
7. The degree of the applicant’s social integration, including language proficiency, professional situation, and social relationships.
8. Ties with the country of destination, including language, cultural belonging, and family connections.
9. The risk of reoffending and the concrete level of threat to public safety.

The Court has emphasised that none of these criteria is decisive in isolation; taken cumulatively, they serve as a guide for determining whether the expulsion decision constitutes a disproportionate interference with the individual’s fundamental rights. This approach exemplifies the Court’s technique of balancing the abstract system of Convention rights against concrete factual circumstances in a principled and transparent manner.

3. The Function of the Proportionality Test

The proportionality test is not a mechanical checklist but a structured exercise of judgment. Its function is threefold.

First, it ensures that expulsion decisions are assessed against the totality of the individual’s circumstances, rather than on the basis of a single factor — whether criminal history, length of residence, or family status. The Court has repeatedly held that expulsion cannot be justified by reliance on any single element in isolation, no matter how significant.

Second, the test operates as a safeguard against arbitrary and discriminatory practice. By requiring national authorities to articulate how the relevant factors have been weighed, the test imposes a discipline of reasoning that renders expulsion decisions susceptible to meaningful judicial review — whether at the domestic level or, ultimately, at Strasbourg.

Third, the test functions as a mechanism of dialogue between the Court and Contracting States. The Boultif–Üner criteria do not prescribe an outcome in any given case; they identify the considerations that States are expected to address. Where domestic authorities have conscientiously applied these criteria, the Court has generally extended a substantial margin of appreciation. Where, by contrast, domestic decisions have failed to engage with the relevant factors, the Court has not hesitated to find a violation of Article 8.

4. Proportionality Beyond Article 8

Although most prominently associated with Article 8, the logic of proportionality permeates the Court’s expulsion jurisprudence more broadly.

Under Article 3 ECHR, no proportionality assessment arises at the level of the right itself — the prohibition is absolute, and, as Chahal and Saadi make clear, the gravity of the threat posed by the applicant cannot be balanced against the risk of ill-treatment. Nevertheless, proportionality-type reasoning operates within the assessment of whether the “real risk” threshold is met, as the Court examines the applicant’s individual circumstances alongside the general conditions in the receiving State.

Under Article 5 ECHR, the permissibility of detention in the expulsion context depends on whether the measure remains proportionate to its stated aim — a requirement reflected in the Court’s insistence that proceedings be conducted with due diligence and that detention not exceed a reasonable duration.

Under Article 1 of Protocol No. 7, the Court’s examination of whether restrictions on procedural guarantees are offset by sufficient counterbalancing safeguards is itself an exercise in proportionality.

Across these provisions, proportionality operates as a unifying analytical principle, ensuring that the Convention’s protections remain responsive to the particular circumstances of each case while maintaining coherence across its various strands.

5. The Multi-Layered Protection of Expelled Foreign Nationals: A Synthesis

Drawing together the themes developed throughout this series, the Convention’s protection of foreign nationals in expulsion proceedings may be conceived as a multi-layered architecture:

• The first layer is absolute: Article 3 ECHR prohibits expulsion where there exists a real risk of torture or inhuman or degrading treatment in the receiving State, regardless of the conduct or status of the individual concerned.
• The second layer is qualified but robust: Article 8 ECHR protects private and family life, subject to the proportionality test set out in Boultif and Üner.
• The third layer is procedural: Articles 5, 13, and — exceptionally — 6 ECHR ensure that detention is lawful and non-arbitrary, that effective remedies are available, and that expulsion does not expose the individual to a flagrant denial of fair trial guarantees in the receiving State.
• The fourth layer is specialised: Article 1 of Protocol No. 7 ECHR provides lawfully resident aliens with specific procedural safeguards, as reinforced in the Court’s recent judgments in Muhammad and Muhammad v Romania and Demirci and Others v Hungary.

Taken together, these layers reflect the Court’s commitment to ensuring that expulsion, while remaining within the permissible exercise of State sovereignty, does not become an instrument of arbitrary, disproportionate, or undignified treatment of those under the jurisdiction of a Contracting State.

Conclusion

The Court’s approach to expulsion is not confined to substantive or procedural guarantees alone; it assesses the effects of such measures on the individual in a multi-dimensional manner, insisting on a dynamic balancing exercise governed by the principle of proportionality. The framework systematised in Boultif and Üner requires that a broad range of factors — the individual’s criminal history, social integration, family situation, and ties with the country of destination — be weighed together.

Through this assessment, the Court monitors whether Contracting States have struck a fair and proportionate balance between their immigration and public order policies, on the one hand, and the fundamental rights of the individual, on the other. In so doing, the Court seeks to prevent expulsion from degenerating into arbitrary or discriminatory practice.

This framework imposes on Contracting States not merely a negative obligation to refrain from expelling refugees but also a positive obligation to ensure that, for as long as refugees and other foreign nationals remain within their jurisdiction, they are afforded an effective and dignified regime of fundamental rights. The substantive and procedural protections examined across this series constitute the foundation of that regime. The companion question — what rights such individuals enjoy in the course of their residence in the host State — forms the subject of a separate study.

¹ Boultif v Switzerland App no 54273/00 (ECtHR, 2 August 2001).
² Üner v Netherlands App no 46410/99 (ECtHR [GC], 18 October 2006).