BOSTON – The court that made Massachusetts the first state to legalize gay marriage will now decide whether same-sex couples from other states can also marry here, even if their home states do not recognize such unions.

Other states are closely watching the case because if the Supreme Judicial Court strikes down a 1913 law, same-sex couples from across the country could come here to wed and demand marriage rights at home.

Eight gay couples from surrounding states, all of whom were denied marriage licenses in Massachusetts, are challenging the law, which forbids nonresidents from marrying here if their union would not be recognized in their home state.

Massachusetts last year became the first state to allow same-sex marriage. Forty-one others have passed laws or constitutional amendments banning it.

Michele Granda, an attorney for the couples, argued before the SJC Thursday that the law “sat on the shelf” unused for decades until it was “dusted off” by Gov. Mitt Romney and used to stop same-sex couples from other states from marrying here.

Granda, a staff attorney with Gay & Lesbian Advocates & Defenders, said the high court, in its historic ruling legalizing gay marriage, found that under the state constitution, same-sex couples had the same right to marry as heterosexual couples.

“Nothing in [that ruling] says that our officials can discriminate simply because officials in other states discriminate,” Granda told the six-judge panel.

Prosecutors argued that the law is being enforced in an evenhanded way for heterosexual and same-sex couples.

Assistant Attorney General Peter Sacks, defending the 1913 law, said Massachusetts risks a “backlash” if it flouts the laws of others states by marrying gay couples from states that prohibit it.

“We’ve got respect for other states’ laws,” he said.

The SJC took the case under advisement and is likely to issue a ruling in the next few months.

Plymouth Town Clerk Laurence Pizer said the law puts him in an uncomfortable position when same-sex couples from other states come into his office seeking marriage licenses.

“I’m a town clerk and I discriminate,” Pizer said at a news conference after the SJC hearing.

A group of 13 clerks also sued over the 1913 law, but a lower court said they did not have the right to challenge orders of state officials on constitutional grounds. The clerks, backed by the American Civil Liberties Union, are appealing that ruling.

The eight couples who sued are from Connecticut, Rhode Island, New Hampshire, Vermont, Maine and New York.

Sandi and Bobbi Cote-Whitacre of Essex Junction, Vt., have been together since 1967 and have a recognized civil union in their home state – one of two that allows them. But they said it’s not the same as marriage.

“The civil union gave us state benefits, but we grew up believing that you find someone you want to spend the rest of your life with and you get married,” Sandi said. “In reality, after 38 years, I’m her wife and she’s mine. We want the [marriage] document.”

After same-sex marriage became legal in May 2004, Romney ordered city and town clerks to enforce the law and wrote to every other governor in the nation that out-of-state gay couples would not be allowed to marry in Massachusetts.

A handful of communities initially defied the ban, but eventually capitulated.

A Superior Court judge upheld the law last year, saying that while she was troubled by the state’s decision to suddenly begin enforcing it, the law was not discriminatory because the state has reason to ensure that marriages in Massachusetts are valid in other states.

The plaintiffs asked the state appeals court to hear the case, but the Supreme Judicial Court decided earlier this year to reach down and take the case.