The California Supreme Court on Tuesday ruled that Proposition 8, the successful California ballot measure which defined marriage to be between a man and a woman, is constitutional. It also decided that the some 18,000 homosexual “marriages” contracted in the state should remain valid in law.

By a vote of 6-1, the state Supreme Court justices ruled Proposition 8 was constitutional. The court unanimously ruled that existing “marriages” would stand.

Proposition 8 was put forward as a response to the California Supreme Court’s May 2008 decision which by a vote of 4-3 overturned a state ban on such unions.

Chief Justice Ronald M. George authored the majority opinion in today's court decision.

The court rejected Prop. 8 opponents’ “principal argument,” which was that the proposition was not a constitutional amendment but rather a constitutional revision. A revision may only be proposed in a state constitutional convention.

The justices said that Prop. 8 “does not entirely repeal or abrogate” same-sex couples’ state constitutional right of privacy and due process. Rather, it “carves out a narrow and limited exception to these state constitutional rights” by reserving the designation of the term “marriage” for “opposite-sex couples.”

Proposition 8 left “undisturbed” what the court called the “extremely significant substantive aspects” of a same-sex couple’s constitutional right to establish an “officially recognized and protected family relationship.”

Concerning the validity of homosexual “marriages” contracted after the court’s May 2008 decision but before the passage of Proposition 8, the court said the law cannot be “properly interpreted” to apply retroactively.

“Accordingly, the marriages of same-sex couples performed prior to the effective date of Proposition 8 remain valid and must continue to be recognized in this state,” the court’s decision read.

According to the Los Angeles Times, the only dissenting vote on the constitutionality of the measure was cast by Justice Carlos R. Moreno, the only Democrat on the court. Justice Moreno sided with the argument that Prop. 8 was a revision rather than an amendment.

Andrew Pugno, the General Counsel of Prop. 8 backer ProtectMarriage.com, said in a Tuesday statement that the group was “very gratified” that the ballot measure was upheld.

“This is the culmination of years of hard work to preserve marriage in California. Hundreds of thousands of volunteers worked diligently to uphold the institution of marriage. Twice, voters have decided that marriage in California should be only between a man and a woman.

“We are extremely pleased that the Supreme Court has acknowledged the right of voters to define marriage in the California Constitution. The voters have decided this issue and their views should be respected.”