Brown's reasoning would confer upon the state Supreme Court power it has never had, attorneys Kenneth Starr and Andrew Pugno said in their response to the attorney general's December brief.

Brown "is inviting this court to declare a constitutional revolution," the attorneys argued in the 29-page response. "His extra-constitutional vision is one of unprecedented judicial hegemony, a sweeping power vested in the least-democratic branch that overrides the precious right of the people to determine how they will be governed."

Prop. 8, passed by voters 52 to 48 percent in November, was a constitutional amendment that defined marriage as being between one man and one woman. It was designed to overturn the state Supreme Court's decision in May that called marriage a constitutional right and opened the way for an estimated 18,000 same-sex marriages in California.

Prop. 8 was challenged by opponents of the marriage ban immediately after the election. But Brown, the state's top lawyer, raised the stakes when he took the unusual step of refusing to defend the voter-passed initiative in court and instead challenged it on his own constitutional grounds.

Because the court's May ruling equated a person's right to marry with the rights to liberty and privacy, it should be recognized as an inalienable right that voters can't generally overturn, Brown said in his brief.

It would be "tyranny of the majority" to allow such rights to be taken away by a simple majority vote, he said, arguing that such an action is "inconsistent with the guarantees of individual liberty in the state Constitution."

But Prop. 8 proponents said Monday that Brown was carving out law where none existed. They argued that if the attorney general's argument prevailed, it would be virtually impossible for voters to amend the state Constitution whenever the courts determined that inalienable rights were involved.

"The attorney general's theory would fundamentally alter the role of the California judiciary," said the attorneys for ProtectMarriage.com, the official proponents of Prop. 8.

"If the (initiative) process is done correctly, once the Constitution is changed, that's the document the judges work from," Pugno said in an interview. "This would put the court above the reach of the people when it came to amending the Constitution."

But Brown refused to back away from his stand, arguing that concerns about individual rights can and should trump the initiative process in most cases.

"People have a right to amend the Constitution," he said in an interview Monday. "But when it comes to dealing with basic liberties, they should have to demonstrate a compelling interest that it needs to be done for the good of the community."

In his brief, Brown did not challenge the validity of Prop. 8 itself, arguing against legal challenges by opponents who called the initiative a wide-ranging revision of the Constitution rather than a simple amendment. He did, however, support the validity of the 18,000 marriages that took place while same-sex weddings were legal in the state.

Prop. 8 supporters have asked the high court to void those marriages.

In a reply brief filed Monday, San Francisco City Attorney Dennis Herrera challenged the arguments made by Prop. 8 supporters, arguing that they want the court to issue "a blank check to discriminate - a judicial declaration of open season on disfavored minority groups."

Herrera's brief, filed on behalf of 15 local governments and seven married couples, is part of a flood of legal papers expected to be filed in the next few weeks as parties on both sides of the same-sex marriage debate rush to put their ideas in front of the state Supreme Court.

By Jan. 21, attorneys both for and against Prop. 8 will file their final briefs, which the court will consider before a hearing on the case, which could come as soon as March.

E-mail John Wildermuth at jwildermuth@sfchronicle.com.

This article appeared on page A - 1 of the San Francisco Chronicle