Systematic amendment to the adoption-based nationality regime raises well-founded doubts of constitutionality

On the 19 May 2026, the amendments to the Nationality Act (Law no. 37/81, of 3 October), introduced by Organic Law no. 1/2026, of 18 May, entered into force. These amendments include a systematic modification with significant impact on the regime governing the acquisition of Portuguese nationality by adoption.

Pursuant to Article 3 of the said statute, Section II of Chapter II is deleted, and Article 5 is moved to Section I, concerning acquisition of nationality by effect of will.

Although formally presented as a mere systematic reorganization, this amendment substantively amounts to a modification of the legal framework governing the acquisition of nationality by adoption.

Indeed, the legislator had, until now, autonomously regulated Article 5 in a separate section, removing it from the general regime governing opposition to the acquisition of nationality, a solution that reflected the material specificity of adoption within the legal concept of filiation.

This normative option was grounded in a structuring principle of the Portuguese legal system: the full equivalence between adoptive filiation and biological filiation.

Under the Nationality Act, acquisition of nationality by adoption requires that the adoptive parent be a Portuguese citizen.

However, with the new systematic insertion of Article 5 within the framework of acquisition by effect of will, the acquisition of nationality by adoption now becomes, in abstract terms, subject to opposition, thereby opening the possibility of a differentiated legal treatment of materially equivalent situations:

• The biological child of a Portuguese citizen acquires nationality by origin, without any possibility of State opposition;
• The adopted child of the same Portuguese citizen may have the acquisition of nationality made dependent on the absence of State opposition, solely on the basis of the adoptive nature of filiation.

Such a solution raises well-founded doubts as to its conformity with the Portuguese Constitution, particularly considering the principle of equality, the principle of full equivalence between adoptive and biological filiation, and the principle of the best interests of the child and protection of family unity.

Furthermore, the amendment in question may represent a regression in relation to the legislative, doctrinal, and jurisprudential development consolidated over recent decades in the Portuguese legal system, which has been consistently oriented towards the full equivalence between adoption and natural filiation, currently constituting a structuring principle of family law and child protection.

Given the significance of the legal and human implications arising from this amendment, as well as the substantial indications of material unconstitutionality it raises, it is necessary to await the manner in which the Administration and the courts will interpret and apply the new regime.

Nistal & Associados