A federal appeals court on Thursday will hear arguments in a case challenging Oklahoma's ban on gay marriage.

Plaintiffs in the case are a lesbian couple – Mary Bishop and Sharon Baldwin – who filed their lawsuit shortly after Oklahoma voters in 2004 overwhelmingly (76%) approved Question 711, which defines marriage as a heterosexual union and prohibits the state from recognizing gay couples with civil unions.

In January, U.S. District Judge Terence C. Kern declared the ban invalid.

State officials appealed Kern's ruling to the 10th Circuit Court of Appeals in Denver, which last Thursday heard arguments in a similar case challenging Utah's restrictive marriage amendment.

(Related: Utah defends its gay marriage ban in case with far-reaching implications.)

The same three-judge panel is hearing both cases.

Kern ruled that Oklahoma's ban “violates the Equal Protection Clause of the Fourteenth Amendment of the U.S. Constitution by precluding same-sex couples from receiving an Oklahoma marriage license.”

Baldwin told the AP that her legal team was struck by the arguments used by Utah in support of its ban.

“[I]t's the same old arguments they've been using all along that have been so unsuccessful,” Baldwin said. “They make it sound as though there are a limited number of marriage licenses and if they start handing out marriage licenses willy-nilly to same-sex couples, then what is that going to do to procreation? Well, it's not going to do anything to procreation. People who still want to have children will still have children.”

Baldwin said she and her partner planned to travel to Denver on Wednesday.