Officials in Cape Cod's gay tourism mecca of Provincetown (search) voted to offer marriage licenses to out-of-state same-sex couples, potentially setting the stage for another legal battle over gay marriage.

Thumbing their nose at Republican Gov. Mitt Romney's (search) stance, the town's selectmen unanimously decided Monday to issue marriage certificates to all couples as long as they attest that they know of no legal impediment to their union.

Romney immediately issued a statement Monday threatening legal action against city and town clerks statewide who defy his interpretation of the law.

Romney's office has warned clerks that they will be required to seek proof of residency (search) or the intention to move to Massachusetts from all couples -- gay and straight -- who are seeking to marry as of Monday, when same-sex weddings become legal.

"We are a nation of laws," Romney said in the statement. "If they choose to break the law, we will take appropriate enforcement action, refuse to recognize those marriages, and inform the parties that the marriage is null and void."

Provincetown town clerk Doug Johnstone did not return a call for comment early Tuesday, but in the past he has resisted Romney's instructions to obtain proof of residency from couples before issuing marriage licenses.

Romney based his decision on a 1913 Massachusetts law that says couples cannot be married here if such a marriage would be void in the state in which they live. And no other state currently recognizes gay marriages.

But the Provincetown Board of Selectmen said gay couples who live outside Massachusetts and have no intention of moving here will still be issued marriage licenses, as long as they attest that they know of no legal impediment to their union.

Huge crowds are expected in Provincetown on Monday, the day that the decision by the Supreme Judicial Court, the state's highest court, takes effect that legalizes gay marriage in Massachusetts. For months, business owners and hoteliers in the gay-friendly seaside town at the tip of Cape Cod (search) have been preparing for an anticipated summer rush of gay weddings.

Romney's office has said the consequences of an illegal marriage could be severe for the couple, particularly if they have children, because of legal questions of support and custody.

There also could be legal consequences for the clerks. Under state law, officials who issue a license "knowing that parties are prohibited" can face a fine of $100 to $500 or a prison sentence of up to a year.

Attorney Mary Bonauto, who represented several gay couples whose case led to the court decision legalizing gay weddings, said Romney's interpretation of state law should bar marriage to gay couples only from those states that have laws on their books that declare gay marriages "null and void." She estimates that only about 20 states have that type of law.

"It's because of his personal beliefs that he is applying the law to all 49 (other states)...," Bonauto said. "I find it sad that the Massachusetts governor would penalize a town for recognizing that Massachusetts has no business denying marriage licenses to same-sex couples whether they are Massachusetts residents or not."

The Legislature has given preliminary approval to a constitutional ban on gay marriage, but it must still receive an additional round of approval from lawmakers during the 2005-2006 session and then by voters in November 2006. The constitutional amendment would simultaneously legalize civil unions.