Despite the success of a ballot measure to change the California Constitution to define marriage as between a man and a woman, legal gay and lesbian weddings performed in the state are still valid.

The California Supreme Court ruled in May that same-sex couples had the right to get married.

An estimated 18,000 gay and lesbian couples took advantage of their new rights until election day on Tuesday.

Voters in the state approved Proposition 8, which will change the constitution and deny marriage rights to same-sex couples.

With 100% of precincts reporting, 52.5% or (5,387,939) voted in favour and 47.5 (4,883,460) against. Opponents of Prop 8 claim “there are more than 3 million and possibly as many as 4 million absentee and provisional ballots yet to be counted.”

The California Secretary of State is expected to reveal today how many votes are yet to be counted as well as where they are from.

In August Jerry Brown, the California Attorney General, told the San Francisco Chronicle:

“I believe that marriages that have been entered into subsequent to the May 15th Supreme Court opinion will be recognised by the California Supreme Court.

“I would think the court, in looking at the underlying equities, would most probably conclude that upholding the marriages performed in that interval before the election would be a just result.”

Gay rights group Equality California and leading LGBT legal groups agree that the marriages performed between June 16th and the passage of Proposition 8 are still valid in the state of California and must continue to be honoured by the state.

The American Civil Liberties Union, Lambda Legal and the National Centre for Lesbian Rights have filed a writ petition before the California Supreme Court urging them to invalidate Proposition 8.

The petition charges that Proposition 8 is invalid because the initiative process was improperly used in an attempt to undo the constitution’s core commitment to equality for everyone by eliminating a fundamental right from just one group – lesbian and gay Californians.

Proposition 8 also “improperly attempts to prevent the courts from exercising their essential constitutional role of protecting the equal protection rights of minorities.”

The groups also claim that radical changes to the organising principles of state government cannot be made by simple majority vote through the initiative process, but instead must, at a minimum, go through the state legislature first.

“There is absolutely nothing in the language of Proposition 8 to suggest that the initiative would apply to couples who have already legally married,” they said in a joint statement.

“Unless the language of an initiative specifically says that it is to be applied retroactively, California’s courts have been very reluctant to do so, especially when the newly passed measure is in such stark conflict with existing constitutional provisions.

“Although it is extremely unlikely that California courts would apply the initiative retroactively, the proponents of Proposition 8 may file a legal challenge trying to invalidate the marriages of those who married before Proposition 8 possibly passed.

“We remain committed to ensuring that all the couples who married in California continue to receive the legal protections and to have their marriages respected as required under California law and will vigorously fight any attempts to take rights away from couples and families.”

Among the couples who got married between June and November were TV star Ellen Degeneres and her partner, actress Portia Di Rossi and Star Trek actor George Takei and partner Brad Altman.