Virginia's definition of marriage is based on “procreation and the ability to procreate naturally,” a lawyer defending the state's ban on gay marriage said Friday.

David B. Oakley, an attorney for court clerks in Norfolk and Prince William County, also said that U.S. District Judge Arenda Wright Allen overstepped her authority when she declared the state's ban invalid last month.

(Related: Judge strikes down Virginia's ban on gay marriage.)

“Judge Allen erred as a matter of law when she awarded Plaintiffs preliminary injunctive relief,” Oakley argued in a brief filed in the Fourth Circuit Court of Appeals. “Although the preliminary injunctive relief was stayed during the pendency of this appeal, if for some reason this matter is remanded, this Court must find awarding a preliminary injunction which alters the status quo and creates a right to same-sex marriage in the Commonwealth which never before existed is clear error and an abuse of discretion.”

Oakley said that states cannot be forced to allow gay couples to marry, adding that clerks could be faced with lawsuits from other people excluded from marriage.

“For example, if the definition of marriage is no longer based on procreation and the ability to procreate naturally, then what is the purpose of prohibiting marriage between persons of close kinship,” Oakley wrote.

A three-judge panel of the appeals court will hear arguments in May. Virginia Attorney General Mark Herring, a Democrat, announced in January that he would not defend the ban in court. He subsequently filed a brief in support of plaintiff couples.