At the height of the Vietnam War in the mid-1960s, anti-war activists in San Francisco circulated petitions to place an initiative on the local ballot urging an immediate cease-fire and American withdrawal from Vietnam. The registrar of voters refused to count the signatures to determine whether the measure would qualify for the ballot. Why? Because he believed the electorate did not have the constitutional power to adopt such an initiative.

The state Supreme Court quickly set the city straight. The registrar's job, the court held, was to administer the laws regarding petitions and the gathering of signatures, not to interpret the constitution.

"It is not his function to determine whether a proposed initiative will be valid if enacted or whether a proposed declaration of policy is one to which the initiative may apply," the court wrote.

That case, Farley v. Healey, is a key part of Attorney General Bill Lockyer's persuasive brief in the current dispute over whether San Francisco can ignore the state's marriage laws because it believes them to be unconstitutional. Lockyer, as the state's chief law enforcement officer, was in a political bind in this case, because his duty required him to confront in court key elements of his own political coalition. But he has pulled off that task neatly.

Lockyer's argument correctly divides the issue, as the court has already signaled it will do. This isn't a case about marriage. Or even civil rights. It's about the duty of city officials to enforce and administer the laws.

You can be for gay marriage, in other words, and still believe that what Mayor Gavin Newsom is doing is wrong. It is wrong because it violates the rule of law and the principles of the separation of powers, which hold that it is the job of the courts to interpret the constitution or declare statutes in violation of it.

The only intellectually consistent challenge to that authority would be a direct assault on the entire tradition of judicial review in the United States. But rather than seek to remove the courts from that role, the city seems intent on joining them.

In the gay marriage case, Lockyer writes, city officials "claim for themselves the judicial power to declare laws unconstitutional, along with the legislative powers to craft an alternative system of marriage. In other words, they claim for themselves, as local ministerial officers, more power than the governor, or the Supreme Court, or the Legislature, because they seek to wield executive, judicial and legislative powers simultaneously." But that position, Lockyer asserts, "is untenable and has no basis in law." It is untenable because, if allowed to stand, Newsom's action would lead to legal chaos, as local officials throughout the land felt free to ignore any law with which they disagreed.

Lockyer's brief also deals deftly with another case that the city, in its filing before the court, raised in its defense. In a footnote to a 1976 case involving the Southern Pacific railroad, the state Supreme Court held that the Public Utilities Commission had the authority to determine the constitutionality of state laws. Now San Francisco officials say that ruling applies to them as well.

But the footnote in Southern Pacific was narrowly construed by the courts for only two years, then flatly overturned by the voters. San Francisco's claim that the new, voter-approved provision doesn't apply to them because they are not an administrative agency of the state is not convincing. The courts, Lockyer points out, have consistently held that cities, and especially counties, are equivalent in many ways to state agencies.

In the handling of marriage applications, this is especially true. The state occupies the entire field of law, setting the rules, drawing up the standard forms used for licenses and requiring that all unions be recorded by county officials with a state office that tracks them. The county's role is purely ministerial.

Lockyer's brief cleverly quotes from the late Justice Stanley Mosk, a liberal icon and civil rights pioneer whose 37 years on the court are a California record. In the Southern Pacific case, Mosk addressed the very issue that Newsom is claiming for cover, the obligation of a public official to uphold the constitution.

"If a commissioner swears to obey the constitution, according to this argument, then he cannot be expected to enforce a law believed to be unconstitutional," Mosk wrote.

But that contention is flawed, Mosk held, because it equates the duty to uphold the constitution with the duty "to declare laws with which he is unsympathetic to be unconstitutional." He concluded: "The oath of office to obey the constitution requires obedience to the constitution not as self-indulgently defined by the commission, but as interpreted by objective judicial tribunals."

California voters have adopted a measure declaring marriage to be a union between one man and one woman. If Newsom or anyone else believes that law to be in violation of the constitution, they can sue to overturn it. Simply ignoring it, or declaring it unconstitutional and substituting their own preferred version of the law in its place, won't do.