BOSTON (AP) – Launching the next battle in the legal war over gay marriage, eight couples and 12 municipal clerks said Thursday they will file lawsuits challenging the 1913 law used to block out-of-state same-sex couples from marrying in Massachusetts.

The groups said they would file two lawsuits in Suffolk Superior Court on Friday, claiming the law, which bars couples who resident outside of Massachusetts from marrying if their marriages would be illegal in their home states, is unconstitutional and that it is discriminatory to enforce it against same-sex couples.

Gov. Mitt Romney and Attorney General Tom Reilly cited the law – which some say was originally written to be used against interracial couples – in denying marriage licenses to out-of-state gay couples.

After gay marriage became legal in Massachusetts last month, several city and town clerks openly defied them and issued the documents to nonresidents anyway, until Reilly ordered them to stop or face penalties.

“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 Thursday.

Romney’s office referred questions to Reilly’s office, which declined comment. In his letter to clerks ordering them to stop issuing the licenses, Reilly said doubts by public officials about the constitutionality of the law were not grounds to stop enforcing it.

The state’s Supreme Judicial Court ruled last November that same-sex couples had a right under the Massachusetts Constitution to marry, and ordered that weddings could begin taking place May 17.

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. Several have family roots here.

Provincetown, the gay 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 denying licenses to out-of-state couples based on the 1913 law.

Somerville, just north of Boston, also married out-of-state couples. The city’s mayor, Joseph Curtatone, said using the law to deny marriage licenses was “not only unconstitutional but simply outrageous.”

“We’ve been out on the lead of this issue from the beginning because we want to treat people equally,” Curtatone said. “We’re confident we’re on the right side of the law.”

Advocates say the segregation-era law has its roots in racism and should not be used to discriminate against gays.

Heterosexual couples from out-of-state were rarely, if ever, challenged over the past several decades. Issues such as whether they were cousins or if they were married to other people could make their marriages illegal in Massachusetts.

Harvard University law professor Randall Kennedy, who appeared at the news conference with the municipal officials and gay couples, said the 1913 law had “regrettable, tainted origins” and grew out of “popular revulsion” over interracial marriages. A similar law was passed by Vermont in 1912.

The attorney general has said there is no evidence that lawmakers were motivated by the race issue in passing the law.

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.

None of the couples involved has current plans to challenge the marriage laws in their home states, attorneys said.

Lee and Judi McNeil-Beckwith, of Providence, R.I., were married May 20 in Worcester. They were both born and raised in Massachusetts and are both licensed nurses in the state.

“We met here, we fell in love here and we got married here,” Lee McNeil-Beckwith said. “Twenty miles shouldn’t make a difference.”

AP-ES-06-17-04 1612EDT