BOSTON (AP) – Eight same-sex couples and 12 municipal clerks are mounting a legal challenge to the 1913 law used to block same-sex couples from other states from marrying in Massachusetts.

The groups filed two lawsuits claiming the state law is unconstitutional and that it is discriminatory to enforce it against same-sex couples.

After the state’s Supreme Judicial Court ruled in November that same-sex couples had a right to marry, Gov. Mitt Romney used the 1913 law to block out-of-state couples from exchanging vows in Massachusetts.

The law says marriages by nonresidents will not be recognized if their union is not legal in their home state. Several city and town clerks openly defied the order to deny marriage licenses to same-sex couples.

“The governor simply can’t dust off this law to discriminate against gays and lesbians,” Michelle Granda, a lawyer for Gay and Lesbian Advocates and Defenders, which represents the eight out-of-state couples, said at a news conference.

Romney’s office referred questions to Reilly’s office, which declined comment.

Nearly 2,500 gay and lesbian couples applied for marriage licenses in the first week that Massachusetts extended the right to same-sex couples last month, according to a survey published by The Boston Globe. Among them were 164 out-of-state couples.

The eight plaintiff couples come from the five other New England states and New York. Some have already gotten married in Massachusetts while others applied for licenses and were denied.

“We have been married in everything except name. We want the peace of mind of marriage,” said Sandi Cote-Whitacre of Vermont, who married Bobbi Cote-Whitacre, her partner since 1967, in Provincetown on May 18.

Provincetown, the gay and lesbian tourism Mecca at the tip of Cape Cod, is the lead plaintiff in the lawsuit filed by the 12 city and town clerks. The town was among the first to defy the governor and issue licenses to nonresidents.

The clerks claim they could be subject to discrimination lawsuits if they are forced to continue to deny licenses to out-of-state couples based on the 1913 law.

Several cities and towns issued licenses to out-of-state couples until the governor, a Republican opposed to same-sex marriage, warned clerks the state wouldn’t recognize them. Attorney General Tom Reilly issued cease-and-desist letters.

Overturning the law could lead large numbers of gays and lesbians to come to Massachusetts to get married. Those couples could then demand legal recognition in their home states, setting off challenges to marriage laws across the country.