The case was brought by Adrian Coman when his partner Robert (Clai) Hamilton, who he married in Brussels in 2010, was denied residency in Romania on the basis it does not recognise same-sex unions.
Romanian officials had argued that the American was not entitled to the EU residency rights awarded to spouses under EU freedom of movement rules.
However, on Tuesday the European Court of Justice said the term “spouse” was gender neutral.
Following the judgement, Coman said: “We can now look in the eyes of any public official in Romania and across the EU with certainty that our relationship is equally valuable and equally relevant.
“We are grateful to the EU court and to the many people and institutions who have supported us, and through us, other same-sex couples in a similar situation,” he said, adding: “It is human dignity that wins today.”
ECJ judges reasoned: “A member state cannot rely on its national law as justification for refusing to recognise in its territory, for the sole purpose of granting a derived right of residence to a third-country national, a marriage concluded by that national with a Union citizen of the same sex in another member state in accordance with the law of that state.
“Accordingly, an obligation to recognise such marriages for the sole purpose of granting a derived right of residence to a third-country national does not undermine the national identity or pose a threat to the public policy of the member state concerned.”
It concludes: “The fundamental right to respect for family and private life being guaranteed by Article 7 of the Charter, the court notes that it is also apparent from the case law of the European Court of Human Rights that the relationship of a homosexual couple may fall within the notion of ‘private life’ and that of ‘family life’ in the same way as a relationship of a heterosexual couple in the same situation.”