The ruling elated gay rights advocates even as the state government and conservative groups began preparing for the inevitable appeal.

If upheld by higher courts, the ruling would make the Golden State the nation's second — after Massachusetts — to authorize same-sex matrimony. And marriage is a state issue. It doesn't belong to federal government or to local officials.

Granted, San Francisco Mayor Gavin Newsom's move last year was a bold one that put the issue front and center in California; but cities and their officials shouldn't have the power to usurp state law. That is a recipe for chaos.

"It appears that no rational purpose exists for limiting marriage in this state to opposite-sex partners," San Francisco Superior Court Judge Richard Kramer, a Republican appointed by Gov. Pete Wilson, wrote in his 27-page ruling, finding the ban denies same-sex couples equal protection under the law.

Kramer's ruling does not reinstate almost 4,000 marriages performed in San Francisco last February and March and voided on Aug. 12 by the state Supreme Court, which found that city officials exceeded their authority by defying state laws. The court did not rule on the constitutional issue. It eventually could let those couples and many more wed legally.

But now the issue is in the proper venue, the courts. This is the first in many steps. Next the ruling will be appealed to the state Court of Appeal in San Francisco, and may be headed eventually to the state Supreme Court.

On Monday at Stanford University, Gov. Arnold Schwarzenegger said he had hoped that the court would uphold 2000's Proposition 22, which reaffirmed the state's definition of marriage as a union between a man and a woman but did not change the state Constitution.

"I believe in what we have now, which is domestic partnership rights,"

The Legislature had passed one of the most sweeping civil unions bills that Attorney General Bill Lockyer cited that as evidence that California does not discriminate against gays. But the judge rejected that argument, citing Brown v. Board of Education: "The idea that marriage-like rights without marriage is adequate smacks of a concept long rejected by the courts — separate but equal."

Opponents are considering going to the ballot to make the same-sex marriage ban a constitutional amendment.

Advocates hailed the ruling as the first step toward a civil-rights milestone.

But judicial activism is not a bad thing. We hope the U.S. judiciary is filled with activist judges when it comes to the Constitution, otherwise judges would be derelict in their duties. The Constitution has always been about extending rights, not restricting them.

Several lawsuits filed by the state and conservative organizations were consolidated before Kramer, a 57-year-old Roman Catholic.

In his ruling, Kramer wrote, "The state's protracted denial of equal protection cannot be justified simply because such constitutional violation has become traditional. Simply put, same-sex marriage cannot be prohibited solely because California has always done so before."

The ban's defenders claimed marriage's main purpose is procreation. But Kramer noted "the obvious natural and social reality that one does not have to be married in order to procreate, nor does one have to procreate in order to be married."