The ruling overturning California's ban on gay marriages is a key and welcome step forward in what promises to be a lengthy legal process.

In voiding Proposition 8, U.S. District Judge Vaughn Walker said the voter-approved ban singled out gays and lesbians for denial of a marriage license, thus violating their constitutional guarantees to equal protection and due process.

Walker's interpretation of the law is exactly right.

"The evidence shows Proposition 8 does nothing more than enshrine in the California Constitution the notion that opposite-sex couples are superior to same-sex couples," Walker wrote in his ruling.

Proposition 8 proponents will no doubt appeal, and the case may end up before the U.S. Supreme Court. Some are already expressing outrage at what's being called judicial activism, with a federal judge daring to overturn the will of the people who voted against gay marriage.

But they are wrong to frame this as Californians vs. Judge Walker. This is the will of one state's voters vs. the law of the land, the U.S. Constitution. On that score, judges are the proper arbiter in such disputes.

To be sure, voters and others across the country are entitled to their beliefs - religious, moral, or otherwise - when it comes to opposing same-sex marriage. But as Walker's ruling suggests, they cross a line when turning those beliefs into discriminatory actions.

Walker has decades of Supreme Court case law on his side: In 1967, the court overturned prohibitions of interracial marriage; in 1978, it declared unconstitutional a Wisconsin law preventing child-support scofflaws from marrying; in 1987, it struck down a Missouri law that said imprisoned felons couldn't marry; in 2003, it ruled that states could not outlaw consensual homosexual activity.

"Decisions of this court confirm that the right to marry is of fundamental importance for all individuals," the court wrote in 1978.

Thus there will be a high hurdle for those who seek to reinstate California's ban. There is not much from their side for higher courts to review, as they called only two witnesses. "Proponents' evidentiary presentation was dwarfed by that of plaintiffs," Walker noted in his opinion.

Any final ruling of course will be bigger than one case in California. Thirty states have prohibitions similar to Prop 8, while five states and the District of Columbia recognize same-sex marriage.

If Walker's ruling is ultimately upheld, a host of difficult questions will have to be confronted. In particular, how will the rulings impact churches and religiously affiliated social-service agencies?

Best to start thinking through those issues now, because, as Ted Olson, one of the plaintiffs' lawyers said, "With this decision we are well on our way to an ultimate victory."