Gay and lesbian couples who legally married in California earlier this year are being targeted by supporters of a ballot proposition that removed the right to same-sex marriage in the state.

The Protect Marriage coalition supported Proposition 8. It passed in November, putting an end to gay marriages. In May the California Supreme Court ruled that to deny gay and lesbian couples the right to marry was unconstitutional.

Around 18,000 same-sex couples got married between June 16h and the November vote.

On Friday the Protect Marriage petitioned the court to annul those marriages.

“Proposition 8′s brevity is matched by its clarity,” it said in its legal brief.

“There are no conditional clauses, exceptions, exemptions, or exclusions: Only marriage between a man and a woman is valid or recognised in California.”

The state Attorney General had previously stated that no marriages would be invalidated by Prop 8. He has now asked the state Supreme Court to invalidate the ballot measure.

“Proposition 8 must be invalidated because the amendment process cannot be used to extinguish fundamental constitutional rights without compelling justification,” Attorney General Edmund Brown said.

In this case, Attorney General Brown said that existing case-law precedents of the Court do not invalidate Proposition 8 either as a revision or as a violation of the separation-of-powers doctrine.

But this does not resolve the matter.

In the In re Marriages Cases, the Court held that article I, section 1 of the California Constitution provides a right to marry that cannot be denied to same-sex couples.

Attorney General Brown argued in a brief to the Supreme Court released on Friday that in order to invalidate such a fundamental right, the Court must determine that there is a compelling justification to do so.

But in the In re Marriage Cases, the court found that no such compelling justification exists.

Gay rights advocates filed lawsuits questioning the legality of Prop 8 within hours of it passing, with 52% of the vote, on November 4th.