Court arguments over Oklahoma's ban on same-sex marriage will center on whether voters singled out gay people for unfair treatment when they overwhelmingly defined marriage as a union between one man and one woman.

Judges at a federal appeals court in Denver will hear arguments Thursday from lawyers representing a couple challenging Oklahoma's ban and the Tulsa County clerk who refused to grant them a license. The judges heard a similar case from Utah last week.

Oklahoma voters approved the ban in 2004 by a 3-1 margin. The Tulsa couple tried to obtain a marriage license shortly afterward.

A federal judge overturned the ban in January, saying it violated the equal-protection clause of the U.S. Constitution. Lawyers for the state say voters have a right to set their own laws.