On 19 November 2025, fifty members of the Assembly of the Republic requested a preventive review of the constitutionality of the 1981 Portuguese Nationality Law, as amended by Decree No. 17/XVII, submitted to the President of the Republic on 11 November 2025 for promulgation as an organic law. The parliamentarians argued that the amendment violated multiple constitutional principles, including the principle of proportionality, the prohibition of automatic penalties, the protection of stateless persons, the restriction of rights without a clear legal basis, the prohibition of deprivation of nationality for political reasons, the principle of personal responsibility for sanctions, the protection of legitimate expectations, the principle of equality, and the prohibition of retroactive laws restricting rights, as enshrined in Articles 16, 17, 18, 26 and 30 of the Constitution and relevant international conventions.

The Constitutional Court declared unconstitutional the requirements that applicants must not have been convicted of a prison sentence of 2 years or more; must not display conduct rejecting membership in the national community, including relying on a previous conviction as evidence of such rejection; and the exception to the consolidation of Portuguese nationality through bona fide possession for ten years where that nationality had been obtained in a manifestly fraudulent manner.

Regarding the claim related to the protection of stateless persons, the court summarised it as that Article 6(3) of the amended Nationality Law required stateless individuals to have 4 years of legal residence to acquire Portuguese nationality while no legal framework existed for stateless persons to obtain such residence. The Constitutional Court observed that citizenship, as a fundamental right under Article 26(1) of the Constitution, enjoys enhanced constitutional protection. It specified this protection to mean that any restrictions must comply with the principles of necessity and proportionality, fall within the absolute reserve of organic law which requires a qualified parliamentary majority, and are subject to preventive constitutional review. The court further held that nationality, as a fundamental right, is directly applicable and binding on all public authorities and private parties, it encompasses not only the right not to be arbitrarily deprived of nationality but also a right of access to Portuguese citizenship for individuals who have a legitimate expectation of acquiring it.

The Constitutional Court recalled that the legislature is bound by Articles 4 and 26 of the Constitution and by international law, including Article 15 of the Universal Declaration of Human Rights, which recognises the right to a nationality and prohibits arbitrary deprivation thereof, and must be taken into account by the interpretative mandate comprised in Article 16 of the Constitution. The court then addressed the specific obligations arising from the 1954 Convention relating to the Status of Stateless Persons and the 1961 Convention on the Reduction of Statelessness. It noted that Article 32 of the 1954 Convention requires States to facilitate the expedited naturalisation of stateless persons. It also referred to Article 20(1) of the Treaty on the Functioning of the European Union, the EU Charter of Fundamental Rights, and the Council of Europe's 1997 European Convention on Nationality, which requires States to facilitate the acquisition of nationality by stateless persons and limits the residence requirement for such applicants to a maximum of 10 years before the application.

The Constitutional Court noted that the objection to the 4-year preferential naturalisation regime for stateless persons was based solely on the fact that the law required legal residence without the domestic legal system providing a procedure for the recognition of statelessness. The court reasoned that the absence of such a procedure constitutes a distinct legislative shortcoming that might give rise to unconstitutionality by omission, but this could not be assessed within the framework of a preventive review of constitutionality. The court further reasoned that finding otherwise would imply that, until a statelessness determination procedure was established, the legislature would be constitutionally barred from requiring legal residence as a condition for the naturalisation of stateless persons. Conversely, it would mean that the legislature would be obliged to grant nationality to stateless persons who had resided in the country for the required period, even if that residence was not lawful.

Such a conclusion, the court held, does not follow from the above-mentioned international instruments binding on Portugal. The court noted that, on the contrary, the legislature sought to comply with those obligations through Article 6(3) of the amended Nationality Law, which in fact improved the position of stateless persons by reducing the 7 to 10 years minimum required periods of legal residence, and by introducing a preferential regime that did not previously exist. In conclusion, the Constitutional Court found no grounds to declare unconstitutional Article 6(3) of the Nationality Law, as amended by Decree No. 17/XVII.