A little over two years ago in this space, I congratulated California on their judiciary’s decision to allow gay people to marry on equal terms as heterosexuals. When that decision was eventually overturned by a referendum the following November, I was both too delirious with Obama fever and too enraged to write a follow-up post. But today, another congratulations is in order for residents of the Golden State: Judge Vaughn Walker ruled the constitutional amendment banning gay marriage – known as Proposition 8 – unconstitutional.

On it own terms, this is great news, not just for California, but for the cause of marriage equality all across the United States. After several states – Maine, New Jersey, New York – failed to follow through on the promise of marriage equality legislation over the last year, some of the progress of recent years – most notably the legalization of gay marriage in Vermont, Iowa, Massachusetts and New Hampshire – had been tempered. Tonight, as most other nights, my good friend Bryan Borland is right: First and foremost, this means that the momentum is once again with gay people.

I have only skimmed the ruling thus far, but as far as I can tell, Judge Walker absolutely demolishes the Prop 8 proponents case that the existence of married gay couples would somehow represent a threat to the status of heterosexual marriages. Per New York Magazine, Judge Walker put it this way in the conclusion to his ruling: “Proposition 8 fails to advance any rational basis in singling out gay men and lesbians for denial of a marriage license. Indeed 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.” He therefore finds it in violation of the equal protection clause.

Supporters of marriage equality should take this moment to celebrate progress, but the battle over Proposition 8 has just begun. The case is likely to go all the way to the Supreme Court, which raises some interesting questions about the tactics of the Prop 8 lawsuit as well as the ongoing confirmation process for prospective Supreme Court Justice Elena Kagan. There has been a fairly deep tactical divide within the gay rights movement over how wise it was to take the legal route to repeal Prop 8, seeing as it will eventual come down to the center-right majority on the Supreme Court to rule on its constitionality. Many in the movement instead wanted to wait for a chance to overturn it in another referendum in a few years time.

Now that the Prop 8 ruling has landed, however, Kagan’s confirmation will take on renewed significance. Like so much else about Kagan, it’s not immediately clear where she would come down if the case came before the Court. Kagan skeptics like to quote her as saying that “there is federal constitutional right to gay marriage” from her confirmation hearings as Solicitor General, but the context was federal law as it stands today. Judging from her saying that the Don’t Ask, Don’t Tell on gays in the military is “morally wrong”, she seems relatively likely to vote in favor of marriage equality. Either way, it should be interesting to whether or how the ruling from California will affect the final debate and/or vote tally on Kagan. The three remaining Republican senators at least somewhat likely to vote for her – Scott Brown of Massachusetts, George Voinovich of Ohio and Kit Bond of Missouri – are probably under even more pressure than before to vote against her now. Voinovich and Bond are social conservatives, but they both voted for Sonia Sotomayor last year, and since they aren’t seek re-election they could, at least theoretically, buck the party line and vote in the spirit of Senator Lindsey Graham (R-S.C.), who will vote for Kagan out of deference to President Obama. Scott Brown represents one of the most liberal states in the country, and one of the few where gay marriage is legal, so if he wants to have a shot at re-election in 2012, he’d be smart not to let the predictable GOP’s Prop 8 hysteria influence his vote.

If confirmed, the Prop 8 case offers Elena Kagan an excellent opportunity to prove that she has earned all the praise Democratic senators heaped on her for being a bridge-builder and someone who could be able to negotiate new 5-4 majorities in important cases by the power of persuasion and legal argument. Assuming the liberal bloc (Kagan, Sotomayor, Stephen Breyer, Ruth Bader Ginsburg) holds, that leaves Kagan with wooing Anthony Kennedy. Kennedy has a moderate streak, and he has been known to side with the liberals (who aren’t that liberal) on some issues of civil liberties and the like. The fate of Prop 8 likely is in his hands.

Pondering this, read Judge Walker’s ruling and celebrate, fellow friends of fairness, love and equality. But two things should not be forgotten: 1) The fight has just begun, and 2) the self-described “fierce advocate for equality” that currently occupies the White House still doesn’t support gay marriage.