Does the Constitutional Court say that the acknowledgment of children born outside marriage lasts forever?

Legal Brief by Bárbara Figueiredo

On 18 March, the provision contained in paragraph 2 of Article 1859 of the Civil Code was declared unconstitutional with general binding force. This provision establishes that an action to challenge the acknowledgment of paternity may be brought by the acknowledging party at any time. In essence, the Constitutional Court held that the possibility provided for in this rule violates the principles of equality and the prohibition of discrimination against children born outside marriage.

Under the regime set out in the Civil Code, acknowledgment of paternity — a voluntary act through which a father recognizes the paternity of a child born or conceived outside marriage — may be challenged in court at any time when it does not correspond to biological truth. This is not the case for actions challenging presumed paternity of children born during marriage, for which a three-year time limit is expressly provided in subparagraph (a) of paragraph 2 of Article 1842 of the Civil Code.

In Ruling no. 188/2026 of 18 March, the Constitutional Court held that this solution — namely, the non-applicability of limitation periods to actions challenging acknowledgment of paternity when brought by the acknowledging party — is not in accordance with the Constitution, particularly when comparing the two situations, which provide different solutions for the same objective: the restoration of biological truth.

Examining the leading rulings identified by the Public Prosecutor’s Office, the Constitutional Court reiterated the arguments underlying the findings of unconstitutionality in both cases. It concluded that the difference in legal regimes, based on the weight attributed by the legislator to the stability of social and family relationships and to the trust on which they should be grounded in cases involving children born during marriage (where paternity is presumed), on the one hand, and to the public interest in safeguarding biological truth where paternity arises from a free and personal act that contains no objective indications of such correspondence, on the other, amounts to nothing more than unjustified discrimination, “deserving of constitutional censure” in light of the current socio-legal landscape of parentage.

Accordingly, for violating the principle of equality and the prohibition of discrimination against children born outside marriage, the Constitutional Court declared unconstitutional, with general binding force, the provision contained in paragraph 2 of Article 1859 of the Civil Code, which establishes that actions challenging acknowledgment of paternity brought by the acknowledging party are not subject to limitation periods.

Finally, it should be noted that in none of the cases in which this provision was found unconstitutional did the Constitutional Court reach unanimity — with Ruling no. 188/2026 of 18 March itself including three dissenting opinions.