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A court case in Massachusetts (search) could have national consequences on states' decisions whether to recognize gay marriages.

Seven gay couples have filed a lawsuit with the state's highest court challenging the law that forbids gay marriage.

"Each of these couples seeking access to the rights of marriage wants to do so to strengthen his or her own individual family and this government institution of marriage provides enormous protection for families," said Mary Bonauto, an attorney with the Gay & Lesbian Advocates and Defenders (search). "We just think it's time for reflexive discrimination to end."

When Vermont became the first state to allow civil unions, granting gay couples many rights of marriage, people on both sides of the issue predicted it would start a trend. Three years later, Vermont is still the only state to recognize civil unions.

But if Massachusetts becomes the first state to allow gay marriage, going one step further than Vermont, homosexual couples from other states could get a marriage license here that their own states would have to honor.

"Because of the Full Faith and Credit clause of our U.S. Constitution, now those states have to accept those marriage licenses as being valid," said Ron Crews, president of the Massachusetts Family Institute (search).

Crews opposes letting gay couples marry, but instead of fighting it through the court system, he's using a more common route, working through the Massachusetts Legislature to author an amendment to the state Constitution defining marriage as a union that can only exist between a man and a woman.

"We know that 37 states have clear definitions of marriage in their state laws or state Constitutions which say, 'No, we would not recognize these marriages,'" Crews said.

Just this week, Texas became the 37th state to pass a constitutional amendment defining marriage as a heterosexual coupling and refusing to recognize gay unions formed in other states. If Massachusetts lawmakers pass the amendment, it would be the 38th state with a "so-called" Defense of Marriage Act (search), more than enough, Crews said, to meet the two-thirds needed to ratify an amendment to the U.S. Constitution.

"That would stop the debate," he said.

But gay-marriage advocates say the issue won't go away.

"These families still exist and still need some protection that they don't have right now," Bonauto said.

The issue only promises to grow more complicated. The state Supreme Judicial Court could decide in the next couple weeks to allow gay marriage. When it returns in the fall, the state Legislature could vote for a constitutional ban, meaning hundreds of marriage licenses already granted would have to be revoked.

Alisyn Camerota contributed to this report.