"Because of the full faith and credit clause of the Constitution (which makes every state accept ‘the public Acts, Records, and judicial Proceedings of every other State’), gay marriage can be imposed on the entire country by a bare majority of the state supreme court of but one state…. The 1996 Defense of Marriage Act? Nonsense. It pretends to allow the states to reject marriage licenses issued in other states. But there is not a chance in hell that the Supreme Court will uphold it."

So says columnist Charles Krauthammer. Not so fast, contends my colleague Jonathan Rauch: "The U.S. Supreme Court is unlikely to impose one state’s gay marriages on the whole country."

Since columnists disagree, let’s go to the scholars. Professor Lea Brilmayer of Yale Law School sides with Rauch: "Marriages have never received the automatic effect given to judicial decisions. They can be refused recognition in other states without offending full faith and credit," she said in congressional testimony on March 3. But others agree with professor Larry Kramer of New York University’s law school, who wrote in 1997, "States cannot selectively discriminate against each other’s laws, [and] Congress cannot authorize them to do so."

This debate is of more than academic interest. Much of the energy behind the Bush-backed proposal to ban gay marriage by constitutional amendment comes from fear of nationwide imposition of gay marriage by a kind of judicial chain reaction. The same fear gave birth to the federal Defense of Marriage Act of 1996, known as DOMA, which authorizes states to ignore gay marriages performed in other states, and the "little DOMA" laws in 38 states, which declare their intent to do just that.

Is this fear of a nationwide, judicially engineered redefinition of marriage plausible? Yes, somewhat, although it’s likely to take several years if it happens at all. Is the proposed constitutional ban on gay marriage a justifiable response? No, emphatically. There are ways to get the courts out of the gay-marriage business without tying the hands of future voting majorities who may — and, I hope, will — eventually come to see gay marriage as good for us all.

The most direct and sweeping way for the Supreme Court to impose gay marriage is also the least likely. That would be to legalize gay marriage everywhere by announcing that the 14th Amendment’s equal protection clause (or the due process clause, or both), which the Court used in 1967 to strike down laws against interracial marriage, can no longer tolerate the man-woman definition of marriage that has been a cornerstone of civilization for the past few thousand years.

Last June’s decision in Lawrence v. Texas, which used the due process clause to strike down all state laws making it a crime to have gay sex, led Justice Antonin Scalia to suggest in a bitter dissent that the Court had set the stage to declare a right to gay marriage. But there is a big difference between ruling that gays cannot be branded criminals and ruling that they must be given the privileges of marriage. Few serious analysts expect the justices to take that big a leap unless and until public opposition to gay marriage softens to the point that they could pull it off without provoking a firestorm.

The stealthier way to promote gay marriage, and the way that is most feared by opponents, would be the full-faith-and-credit two-step: Step one is for the justices to watch from the sidelines while state courts in Massachusetts and perhaps elsewhere use their state constitutions to impose gay marriage upon their own electorates. Step two would be for the Court to require that other states recognize those marriages and, in the process, to strike down all of the defense-of-marriage acts.

Brilmayer and some others say the justices will not take step two. And the traditional judicial interpretation of the full faith and credit clause is on their side. While the norm has always been for states to recognize marriages celebrated in other states, "the full faith and credit clause has never been understood to require recognition of marriages entered into in other states that are contrary to local ‘public policy’ [representing] deeply held local values," as Brilmayer testified. Under this "public policy" doctrine, states have been free to disregard marriages in other states between first cousins, people too young to marry in their home states, people who remarried after quickie Nevada divorces, and (before 1967) people of different races.

But Brilmayer’s views are disputed by dozens of law review articles arguing that DOMA, the 38 state DOMAs, and (many add) even the long-standing "public policy" doctrine, are all unconstitutional, at least in the gay-marriage context. Gay-advocacy groups have prepared a well-orchestrated litigation campaign to use the full faith and credit clause to force recognition of gay marriages across the country. And Justice Anthony M. Kennedy has provided them with powerful ammunition with his majority opinions in both Lawrence and the 1996 decision in Romer v. Evans, which used the equal protection clause to strike down a Colorado referendum barring adoption of gay-rights laws anywhere in the state. Both decisions held that animus against homosexuals — which Scalia called "moral disapprobation" — is an irrational and illegitimate basis for some, if not necessarily all, anti-gay laws. It would not be a great leap to extend this logic to strike down DOMA and its state-law clones, and then to carve a gay-marriage exception into the public policy doctrine.

"The prophecies of what the courts will do in fact, and nothing more pretentious, are what I mean by the law," Justice Oliver Wendell Holmes Jr. once said. In that spirit, I prophesy that Kennedy, his four more-liberal colleagues, and possibly Justice Sandra Day O’Connor, will seek to promote gay marriage but will proceed cautiously, with their fingers to the winds of public opinion. They may begin by issuing narrowly drawn decisions enforcing state court judgments — which other states have almost always been required to honor — such as judicially approved property settlements in divorce decrees growing out of Massachusetts gay marriages. And when these justices sense that the time is ripe — assuming that those who remain on the Court have the votes — they will apply the full-faith-and-credit two-step to ban states from discriminating against other states’ gay marriages in any way.

This prospect leaves me quite conflicted. While I strongly support gay marriage, I oppose its imposition by judicial fiat. And while judicial activism at its best can build public consensus for long-overdue reforms, I am concerned that the courts have increasingly crossed the line from exercising healthy activism into usurping legislative powers, disdaining representative government, and casually casting aside tradition in the guise of interpreting the Constitution.

So I have some sympathy for the idea of amending the Constitution to prohibit any judicial decision construing that document to require recognition of any gay marriage. (The problem of state courts in Massachusetts and elsewhere inventing state constitutional rights can and should be handled at the state level.) Because amending the Constitution is a grave step that risks unintended consequences, I am not yet ready to support that approach, as long as the Supreme Court proceeds cautiously and incrementally on gay marriage. But a sudden, broad decision requiring all other states to honor Massachusetts’ gay marriages, for example, might persuade me that the time has come to reclaim some of the rights of the people to govern themselves.

By no stretch of the imagination, however, is the proposed amendment behind which Bush has placed his prestige an appropriate way to protect representative government. Quite the contrary. The first clause of the so-called Musgrave amendment (sponsored by Rep. Marilyn Musgrave, R-Colo.) would impose a uniform federal definition of marriage upon the whole country: "Marriage in the United States shall consist only of the union of a man and a woman." This amounts to an anti-democratic, anti-federalist effort to ban all state legislatures, for all time, from experimenting with gay marriage — even if and when most voters in most states come to support gays’ right to wed. And public opinion appears to be headed in that direction: Although polls still show voters opposing gay marriage by a ratio of about 2-to-1, the numbers appear to be softening over time. Especially significant is that young voters are far more open to gay marriage than old ones.

In this sense, the president’s position on gay marriage has something in common with that of the Massachusetts court: Neither is willing to defer to democratic governance. While the court has imposed its definition of marriage on today’s voters, Bush seeks to impose his own definition on their children and grandchildren.