Romania's top court on Wednesday ruled unanimously that a proposed referendum that would define marriage as a heterosexual union in the constitution is valid.

While gay and lesbian couples are not permitted to marry in the socially conservative nation, its constitution says family starts “on the basis of freely consenting marriage between spouses.”

Roughly 3 million Romanians signed a proposal that seeks to replace “spouses” with “a man and a woman.”

LGBT rights activists say the change, if approved, would make it impossible to legalize marriage equality at a future day..

Chief Justice Valer Dorneanu said that the court was only ruling on whether the proposal was legally valid.

“The court had to rule strictly whether the revision proposal was constitutional,” he told state news agency Agerpres.

Romanians could vote on the proposal later this year.