NASHVILLE (AP) - Four same-sex couples who were legally married in other states filed a lawsuit Monday challenging Tennessee's laws that prohibit recognition of their marriages.

The lawsuit, filed in federal district court in Nashville, says Tennessee's laws violate the federal Constitution's guarantees of equal protection and due process, and "the constitutionally protected right to travel between and move to other states."

The U.S. Supreme Court last June struck down the federal Defense of Marriage Act, which defined marriage as the union of one man and one woman. However, the court did not address state bans on same-sex marriage. Under the U.S. Supreme Court ruling, gay couples who are legally married in states that allow it can get the same federal benefits as married opposite sex couples.

In Tennessee, however, marriage between partners of the same gender is prohibited by state law and by a constitutional amendment approved in 20 06. It says that for a marriage to be legal in the state, it must be between a man and a woman.

"All of our plaintiffs are people who were legally married in their states of residence," said Abby Rubenfeld, an attorney for the couples. "The federal government says it's OK ... then they move to Tennessee for job purposes, for whatever, and all of a sudden their marriage isn't recognized."

Veterinarians Sophy Jesty and Valeria Tanco, both plaintiffs in the lawsuit, got married in New York in 2011 and now live in Knoxville where they teach at the University of Tennessee College of Veterinary Medicine.

Tanco is 18 weeks pregnant, but under Tennessee's current law, Jesty wouldn't be recognized as the child's legal parent.

"Val will have a legal parental status based on the fact that she's the one that's carrying our baby, but I will not," Jesty said. "It's a very frightening thing ... to lose your legal rights as a parent."

Chris Sanders, executive di rector of the Tennessee Equality Project, a gay rights advocacy group, said he applauds the plaintiffs' effort because he is contacted every week by gay couples seeking legal recognition.

"We believe it's the first step in knocking down a huge barrier of discrimination in the state," he said.

The filing Monday comes as New Jersey Gov. Chris Christie has decided to drop his legal challenge to same-sex marriage, making New Jersey the 14th state to allow gay marriages.

Rubenfeld, who married under California's same-sex marriage statute, said she hopes her lawsuit puts Tennessee on track to be among the next states to recognize same-sex marriage.

"It doesn't matter what number (we are), we're to be there," she said.