"I believe we should be allowed to marry the person we're in love with ... and we deserve the freedom to do so," plaintiff Marie Carlson said at a news conference, the Milwaukee Journal Sentinel reported. Her suit is supported by the American Civil Liberties Union.
"This constitutional amendment was approved by a large majority of Wisconsin residents," state Attorney General J.B. Van Hollen said in a statement. "I believe the amendment is constitutional, and I will vigorously defend it."
The ACLU's lawsuit argues Wisconsin's gay-marriage ban violates the U.S. Constitution's guarantee of due process and equal protection under the law. It also aims to overturn the state's so-called marriage evasion law, which makes it a crime to travel to another state to get married if that union would not be recognized by the Badger State.
Seventeen states and Washington, D.C., permit gay marriage.