Tuesday's ruling by a panel of three judges of the U.S. Court of Appeals for the Ninth Circuit holding unconstitutional the California ballot initiative that aimed to take the right to marry away from same-sex couples is hardly the last word in the debate. The court's ruling, unlike that of the district court below, did not purport to decide whether states must, in the first instance, give marriage licenses to same-sex couples, but only that, once they do, they cannot take them away for no good reason. Even so narrowed, the proponents of the ballot measure (not the state, which at this point is not defending it) are likely to seek further review by the full panel of Ninth Circuit judges or by the Supreme Court, or probably both.

But it's an important step, and the careful and constrained way that it was done is a study in how judging works. For starters, there was the question of whether, since the state didn't want to defend the law, the proponents of the ballot initiative could step in and do so. The federal court asked the State Supreme Court to answer that question -- since it involves issues of standing to defend state law -- and it said yes. Federalism 101.

The next question was whether the district court judge should have recused himself from even deciding the case because he is gay and in a long-term relationship, facts not disclosed to the parties. The answer to that, hinted at in oral arguments and provided in Tuesday's opinion, was a resounding no. Imagine if black judges were not allowed to sit in civil rights cases if they had ever experienced racism, or if women judges who had had abortions were disqualified from abortion rights cases. Judges are human: multiracial and ethnic and, yes, also heterosexual and homosexual and bisexual. If you ask me, diversity makes a panel better, not weaker. The Ninth Circuit did not disagree.

Then there was the big question. Judge Stephen Reinhardt, one of the nation's leading liberal jurists, a man of courage and conviction and long experience, delivered the opinion for two of the three members of the panel. You might have expected him to go big and broad, to try to "make law" not just for California, but for the country, and maybe not even just for marriage, but for all rights. But that would mean you don't really know Reinhardt. He understands too well how law is done. When pushing the boundaries, you do it one step at a time.

And so Reinhardt, rather than trying to answer the big question, made a point of making it smaller. The court was not trying to decide whether denying same-sex couples the right to marry is unconstitutional, but only whether the act of taking it away is. The argument here was not that California had to change its law to accommodate the rights of gay citizens. It had already done so as a result of a state court decision. The question was whether that right could then be taken away. A state can only act based on a rational and legitimate purpose. It may not have to give you a benefit in the first place, but once it does, it needs a reason to take it away.

Of course, there is overlap between the narrower question and the broader one. My guess is that most of the people who are now nodding their heads in agreement would also agree with those court decisions that have held that, under their state's constitution, discrimination against gays in marriage is itself a denial of equality. And most of us would reach the same conclusion under the U.S. Constitution.

But legal revolutions proceed in steps. That's how change tends to come, when it comes peacefully and with broad acceptance. The Ninth Circuit took the step of saying that California could not take away the right to marry from same-sex couples. Not too long ago, the very idea that any state would grant them such a right would be unthinkable. In the not too distant future, I trust, it will seem strange that it took us this long. This was a step along the path, in the finest tradition of constitutional adjudication.