Mississippi Gov. Phil Bryant has vowed to appeal if a federal judge strikes down the state's ban on gay marriage as unconstitutional.

Last week, U.S. District Judge Carlton W. Reeves heard oral arguments in a case challenging Mississippi's ban.

The lawsuit was filed by the Campaign for Southern Equality (CSE) on behalf of Andrea Sanders and Rebecca Bickett, who wish to marry in Mississippi, and Jocelyn Pritchett and Carla Webb, who want their marriage celebrated in Maine to be recognized by Mississippi.

Arguing for the plaintiffs was Roberta Kaplan, who also led the legal team in the landmark Supreme Court Windsor decision that struck down a critical provision of the Defense of Marriage Act (DOMA) last year. Windsor has played a significant role in cases challenging state marriage bans.

Kaplan sounded upbeat speaking to reporters at the conclusion of the 5-hour hearing.

“Judge Reeves clearly was incredibly well prepared,” Kaplan said. “His questions were all incredibly smart and relevant. He was engaged and motivated.”

Reeves questioned many of the state's arguments, leading The Clarion-Ledger to conclude that he was likely to overturn the ban.

“This is something that the state of Mississippi voted overwhelmingly to support,” Bryant, a Republican, told WAPT News. “And now a federal judge is saying he believes it's unconstitutional. It's in the courts. We'll certainly turn to the attorney general to put up a vigorous defense and appeal.”