SACRAMENTO, CA — On Friday, California Attorney General Jerry Brown urged the state’s Supreme Court to overturn Proposition 8, which adds a state constitutional amendment banning same-sex marriages. The move represented an about-face for Brown, who immediately after voters passed the measure November 4th vowed to defend it.On the same day, a California-based “marriage defense” organization filed a Supreme Court brief requesting annulment of the approximately 18,000 same-sex marriages California sanctioned between the time the state’s Supreme Court ruled a ban unconstitutional in May and November’s vote.

“Proposition 8’s brevity is matched by its clarity,” a legal brief filed by Protect Marriage states. “There are no conditional clauses, exceptions, exemptions, or exclusions: ‘Only marriage between a man and a woman is valid or recognized in California.’”

The group’s action may be part of what changed Brown’s mind. Even though he is required by law to defend state laws like Prop. 8, he repeatedly has stated no existing marriages would be in jeopardy. After further study of the applicable case law and relevant documentation, he said the state’s voters overstepped their bounds in approving Prop. 8.

“Upon further reflection and a deeper probing into all the aspects of our Constitution…it became evident that the Article 1 provision [in the California Constitution] guaranteeing basic liberty, which includes the right to marry, took precedence over the initiative,” Brown told the Los Angeles Times on Friday. “Based on my duty to defend the law and the entire Constitution, I concluded the court should protect the right to marry even in the face of the 52-percent vote” that passed it.

Shannon Minter, legal director of the National Center for Lesbian Rights, characterized Brown’s reversal as extraordinary and hopeful.

“The fact that after looking at this he shifted his position and is really bucking convention by not defending Prop. 8 signals very clearly that this proposition can not be defended,” Minter told the Associated Press.

Of primary concern for Brown — and at issue in the legal challenges same-sex-marriage supporters filed within hours of Prop. 8 passing — is a technical point of law that could mean Prop. 8’s demise. Brown and the proposition’s opponents say Prop. 8 seeks to deprive a minority group of a fundamental right. As such, the controversial ballot initiative is a constitutional revision, not an amendment.

Amendments may be taken directly to voters by petitioning to have them included on a general-election ballot, as was the case with Prop. 8. Revisions, on the other hand, must be proposed first in the legislature or within a constitutional convention, either of which requires a two-thirds majority for approval before the matter can be sent to voters.

“Proposition 8 must be invalidated because the amendment process cannot be used to extinguish fundamental constitutional rights without compelling justification,” Brown said Friday, adding that the Supreme Court’s May decision found no compelling reason for a same-sex-marriage ban. Prop. 8 “deprives people of the right to marry, an aspect of liberty that the Supreme Court has concluded is guaranteed by the California Constitution.”

The distinction in subject matter and format is one of degrees, but if the state’s Supreme Court agrees with Brown and Prop. 8’s opponents, Prop. 8 may be declared invalid.

The court could begin hearing arguments in the challenge as early as March.

Kenneth Starr, dean of Pepperdine University’s law school and the independent counsel who investigated former President Bill Clinton, has signed on to lead the arguments in favor of Prop. 8, the Yes on 8 campaign announced Friday.