BOSTON — Massachusetts Attorney General Martha Coakley says laws in Nevada and Hawaii prohibiting same-sex marriage are unconstitutional.

Coakley is leading a coalition of states in filing a brief with the 9th U.S. Circuit Court of Appeals arguing the laws violate the 14th Amendment of the U.S. Constitution and should be struck down.

Coakley said the experience in Massachusetts, the first state to legalize gay marriage, shows that allowing same-sex couples to marry only strengthens the institution of marriage.

Coakley led the filing of the amicus brief on behalf of Massachusetts and 13 other states, including California, Connecticut, Delaware, Iowa, Illinois, Maine, Maryland, New Hampshire, New Mexico, New York, Oregon, Vermont, Washington state and the District of Columbia.

Hawaii and Nevada provide many protections for same-sex couples, but deny them full marriage status.

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