BOSTON, Mass. (AP) — The shores of Cape Cod and vistas of the Berkshires have long been the backdrop for out-of-state couples exchanging “I do’s.”

But same-sex partners who aren’t from Massachusetts shouldn’t pack their bags with the idea that last week’s gay marriage decision means a walk down the aisle for them, too.

Massachusetts law does not allow nonresidents to get married if the union would not be legal in the state where they live. Only the Bay State has legalized gay marriage.

“Certainly, you couldn’t just come to Massachusetts and say, ‘Hey, I want to get married,’” said Paul Martinek, editor of Lawyers Weekly USA. “My reading is that it’s not going to be easy unless the clerks aren’t diligent and don’t check to see where people are residing.”

Gov. Mitt Romney and several lawmakers are trying to use a court-imposed 180-day waiting period to pass a civil union law, which would convey the benefits and obligations of marriage granted under state law without the title. But many legal experts believe Massachusetts — come mid-May — will host the first same-sex weddings in the United States.

“Couples are going to come to Massachusetts to get married for the same reason they went to Vermont to get civil unions and to Canada to get married, because marriage is such an important right,” said Josh Friedes of the Freedom to Marry Coalition of Massachusetts.

Whether the Massachusetts marriages would be recognized in other jurisdictions is in question because of the Defense of Marriage Acts adopted by 37 other states and the federal government.

According to legal experts, Massachusetts’ restriction on out-of-state residents was placed out of respect for nearby states, which might have different age restrictions or other limitations on marriage. It is rarely invoked because most states have uniform marriage laws.

Determining whether someone lives in Massachusetts, though, is murky process that probably would be left to the city or town clerk.

There is nothing in state law that defines residency as it pertains to marriage, according to legal observers. A couple therefore must only indicate that they are residents and intend to remain residents.

It is unclear what would happen if the day after the marriage, their intentions change and they return to the state they came from.

Plymouth Town Clerk Laurence Pizer, past president of the Massachusetts Town Clerk Association, said he would take a couple’s word.

“History says that it’s not our job to sleuth,” Pizer said. “It’s our job to accept oaths.”

A clerk could be fined if he or she authorized a same-sex marriage knowing the two parties weren’t Massachusetts residents, Pizer said.

Since Vermont approved civil unions in 2000, about two-thirds of the couples who have taken their vows have been from out-of-state.

Vermont lawmakers specifically rejected a provision that would have invalidated any same-sex union of a couple from a state that did not recognize such unions.