Gay couples unsatisfied that their own state forbids them to marry have now taken their battle into Massachusetts, but they have taken the wrong detour.

They argue that a law enacted in 1913 that forbids out-of-state couples – whether heterosexual or homosexual – to marry unless their home state approves is unconstitutional.

But what good would fighting a Massachusetts law do them? No law in this state extends beyond the border, and even if this state allowed out-of-state couples to marry, their marriage wouldn’t even be recognized in their home state.

If out-of-state gay couples wish to marry, they should argue their case in their own state, or put the issue before a federal judge, not before a judge whose decision has no jurisdiction where they live.

A lawyer for the Gay and Lesbian Advocates and Defenders who represents the eight gay couples now in court could argue that the 1913 law may originally have been enacted to prevent interracial marriages from taking place, and is therefore unconstitutional.

But though legal experts agree it was put on the books to bar interracial marriage during the pre-Civil Rights era, and that it should be repealed, it would do little for out-of-state same-sex couples unless those couples decided to move to Massachusetts.

Gov. Mitt Romney’s decision to enforce the early 20th-century law drew much criticism from gay rights activists, but it only obliges same-sex couples to respect the laws of other states. It has little implication for gay couples who want to get married and live in Massachusetts.

Moreover, the federal government should be responsible for regulating such interstate matters, not a Massachusetts judge.

If a tourist in Amsterdam bought marijuana where it was legal, it could not be brought into the U.S. legally. Similarly, out-of-state couples cannot expect their marriages to have meaning outside Massachusetts.

An out-of-state gay couple may have more basis for a civil suit against the government of their home state if they were allowed to marry in Massachusetts, but the SJC would be setting the wrong precedent to repeal the 1913 law, because it would only disrespect the laws of other states.

Though one gay man who has been trying to marry his partner in Maine declares that “what happens in Massachusetts always matters,” he should not take up the court’s resources in a battle that will not allow him to be married and live with his partner in Maine. What happens in Massachusetts may indeed matter – but for now, this is a state-by-state issue that will not matter in Maine.