On May 17 the state of Massachusetts began issuing marriage licenses to same-sex couples.

The very first day indicted two of the most prominent arguments in favor of homosexual marriage. The “conservative” case that homosexual “marriage” would strengthen the overall condition of marriage was completely discredited. And events proved that the federalism argument was almost certainly offered in bad faith by at least some advocates of homosexual marriage.

The “conservative” case for homosexual marriage is most commonly associated with Andrew Sullivan and Jonathan Rauch. They argue that bringing homosexual people into the institution of marriage would provide stability for relationships that desperately need it. The desire to maintain respectability would create an incentive for homosexual men to be less promiscuous and more faithful. Since heterosexual marriage is already plagued by divorce and infidelity, broadening the institution would gain new adherents to the standards of lifelong love.

Skeptics respond that even long-time homosexual couples do not define monogamy in the same way heterosexual couples do. Homosexual relationships tend to find ways to accommodate outside sexual activity. For instance, a Canadian study of self-described committed male homosexuals together for more than a year found that only 25% were completely monogamous. By contrast, more than 75% of married heterosexual men are monogamous. Another study found that most of the self-described committed homosexual couples had had three to five partners during the previous year.

A straight man who had that many partners in a single year would certainly throw his marriage into crisis.

The truth of this difference between homosexual and straight meanings of monogamy became clear on the very first day Massachusetts offered marriage licenses to homosexual couples. The first couple married in Provincetown, Mass., proclaimed the concept of forever to be “overrated” and that “it's possible to love more than one person and have more than one partner.”

This statement reflects an attitude that is different in kind from the occasional infidelity of married couples. It is inconceivable that a straight man would proclaim his right to have more than one partner on his wedding day with his wife beside him as they both smiled for the camera.

Let's hear no more of the “conservative” case for homosexual marriage.

You remember the federalism argument, of course, even though it is so five minutes ago. That was the claim that the definition of marriage should be handled by the states. If one state wants to experiment, fine. If for some strange, unforeseen reason the homosexual marriage experiment goes awry, the other states would learn from the experience.

The first day of homosexual marriage gave lie to this claim, too, when outof-state couples were featured prominently in news accounts of the new law. Provincetown has been a homosexual tourist destination for some time. Naturally, the town hall felt no compunction about giving out marriage licenses to homosexual couples, even to those who would certainly not be considered married in their home states.

It would be bad for business, you know, to discriminate against paying customers and tourists. Even after Gov. Mitt Romney specifically ordered the towns to enforce the law against performing marriages to out-of-state couples, Provincetown persisted.

During the second week of homosexual marriage, California activists let their cat out of the bag. The Williams Project on Sexual Orientation Law and Public Policy, an advocacy group disguised as an academic department at the University of California-Los Angeles, produced a study outlining the fiscal benefits to California from redefining marriage to include same-sex couples. An article in the May 27 issue of the San Diego Union Tribune highlights wedding tourism as one of the major benefits to the state.

Authors R. Bradley Sears and M.V. Lee Badgett argue that California ought to jump at the chance to be one of the first states to permit homosexual marriage, precisely to take advantage of the financial gains from attracting out-of-state same-sex couples.

In other words, the state of California should make a public policy of luring couples to take vows and receive licenses that will certainly not be recognized as valid in their home state. Perhaps the authors want these couples to return to their home states and demand that their California marriage license be recognized. Or perhaps the authors want California to make a public policy of assisting individuals to break the laws of their own state. Either way, this is certainly the end of the federalism argument. These authors at least evidently did not take the federalism argument seriously for a moment.

I have no doubt of the sincerity of commentators such as Andrew Sullivan and Jonathan Rauch, who once seemed to believe that homosexual marriage in one state could be confined there and provide a social laboratory. But I cannot for the life of me see how anyone can continue to believe that such an experiment is possible. The marriage-deconstruction activists, homosexual and straight alike, will not allow the experiment to run undisturbed for the 30 years or more that would be required to learn anything useful from it.

Let's hear no more about federalism as an argument for homosexual marriage.

The issue is whether we want a national policy of marriage as the sexually exclusive union of a man and a woman or a national policy of marriage as the union of any combination of consenting adults with no particular expectation of sexual fidelity. No serious person can believe any longer that a state-by-state policy is possible or that homosexual activists hold the same ideal of “marriage” as everyone else.

Jennifer Roback Morse is a research fellow at the Hoover Institution.