Canada’s recent decision to recognize same-sex marriage has created a frenzy of speculation on the future of gay marriage here in the United States. Both sides of the gay marriage debate now stand at the ready, unsure of exactly what Canada’s decree will mean for all those seeking matrimony. Yet much of the commentary to date concerning the implications of that decision for the U.S. has confused more than clarified. While Canada’s decision may not ultimately affect Ohio’s marriage law, it may well be a barometer for the legal and social pressure about to descend on the U.S.

Part of the difficulty in achieving clarity here is the sensitive nature of the subject. Discussing gay marriage, even in the sterile legal sense, walks along that thin red line between making a point and causing offense—illustrated perfectly in that famous Seinfeld episode in which Jerry emphatically denies that he’s gay, but then quickly adds: "Not that there’s anything wrong with that."

By becoming the third country, behind Belgium and The Netherlands, to legalize same-sex marriage, Canada has coaxed us out on that gossamer thread. Her close proximity, the ease of weekend border travel, and the absence of any residency requirement, has been enough to put the American legal system on high alert for the army of lawyers ready to challenge any U.S. state unwilling to recognize a lawfully wedded Canadian “wife.” The fact that Canada will wed non-Canadian residents means that same-sex partners can now sashay over the Peace Bridge, get hitched, raise a glass of duty-free bubbly, spend a night in Niagara, and return a “married” couple. Indeed, by the time you read this, more than one lucky man will have caught the bouquet—not that there’s anything wrong with that.

Once the couple returns home, however, the legal questions begin. Must their home state treat the couple as married for tax purposes, making medical decisions, and child rearing questions like adoption? Must private employers issue health and other benefits to the new "spouse"?

Until now, these issues were largely settled. A longstanding legal principle allows states to decline to recognize marriages performed outside the state if they are found to violate the state’s strong public policy interest. Historically, these declinations have included cases where the parties are too young, and marriages that violate the state’s views on consanguinity, marriages from countries permitting polygamy, and marriages between same-sex partners.

Congress added an additional layer to the common law exceptions here, enacting the Defense of Marriage Act or "DOMA"—legislation passed in 1996 which effectively recognizes only marriages of the opposite sex for purposes of immigration, income tax, Social Security, and other federal programs, while reaffirming the authority of the respective states to decline to recognize a same-sex marriage made under the laws of another state.

Notwithstanding this legal authority, Canada has likely forced the United States to contend with at least three complex constitutional issues worth discussing. The first and most well known arises under the "Full Faith and Credit Clause"—a constitutional provision requiring states to honor contracts formed under the laws of other states. Suppose a Canadian-wed couple returns home to, say, Vermont, a state already sympathetic to this issue as demonstrated by their law concerning "civil unions," which grants same-sex couples many of the benefits of marriage. Vermont, for example, could affirm gay marriage while stopping short of performing homosexual wedding ceremonies, simply by declining to void legal marriages from across its northern border. As such, marriages could be recognized in the eyes of the state for purposes of local taxes, property ownership, insurance benefits, and medical decision-making. Voila, married, gay, and here to stay—in Vermont. Not that there’s anything wrong with that, eh.

But suppose, for example, after years of marital bliss, the couple tires of Vermont’s verdant hills and heads for the Ohio heartland. And suppose that officials in the Queen City ironically refuse to recognize the matrimony, and deny the couple Ohio’s spousal benefits. Both established law and DOMA anticipated this dilemma and would therefore permit Ohio and all the other states to keep playing by their own marriage rules.

Bringing us to the second issue—federalism. Both sides of this debate find it difficult to imagine being happily married under Vermont law, only to be “single” again in New Hampshire. Many argue for a uniform rule for all fifty, nifty United States—a sentiment embedded in the Full Faith and Credit Clause that helped transform a collection of independent States into one united nation.

Nevertheless, states remain remarkably diverse when it comes to marriage. There is, for instance, no uniform age requirement. Thus, a girl from Mississippi may marry at age 15, and in New Hampshire, boys as young as 14 and girls as young as 13 can get married with parental consent. “Kissing cousins” laws are also a tad different. It’s legal in certain religious contexts, for example, for uncles to marry their nieces in Rhode Island, while Ohio still frowns on that sort of thing. But perhaps it’s best to let local sensibilities decide these things for themselves, and recognize that even under DOMA, there is no “uniform rule.”

The combination of established law and DOMA suggests that gay marriages performed in Canada’s permafrost will not be recognized any time soon under the traditional reciprocity of marriage laws. The story, however, doesn’t end here. Gay marriage appears to be unique among the public policy exceptions, as demonstrated by the sheer force of the gay and lesbian lobby. There aren’t many bumper stickers calling for Ohio to marry a pair of fifteen year olds, or demanding that it recognize more than a man’s familial love for his brother’s daughter.

Given this heightened attention, the real challenge to state-sponsored gay marriages will likely be based on the Equal Protection Clause. The Supreme Court is predicted to cite Equal Protection principles later this week, when it hands down its decision regarding a Texas law that made homosexual but not heterosexual sodomy a crime. Following that decision, it is safe to assume that gay rights groups will bring an action on behalf of a couple married in Canada who are denied the rights and privileges of traditional married couples.

Thus, while Canada is unlikely to bring gay marriage to Ohio, the courts just might—and yes, there is something wrong with that.

Nathaniel Stewart is a contributor to "Legal Approaches to Sexuality" in the forthcoming Encyclopedia of Bioethics, 3d edition.