Christian conservative group the Alliance Defending Freedom (ADF) is representing Arizona in a federal case challenging the state's ban on gay marriage.

According to the Arizona Capitol Times, Arizona Attorney General Tom Horne named ADF lawyers special assistant attorneys general for the case.

A brief filed on Thursday in Connolly v. Roche lists 4 lawyers from the ADF, who argue the state's ban is justified because gay couples cannot reproduce without a third party.

“Only man-woman couples are capable of furthering the state's interest in linking children to both of their biological parents,” the brief states. Gay couples cannot “advance that compelling state interest” because they “can never provide a child with both her biological mother and her biological father.”

The ADF used similar arguments last year when it represented a group of roughly two dozen GOP lawmakers defending New Mexico's ban. The New Mexico Supreme Court struck down the ban in December.