A Kentucky clerk who stopped issuing marriage licenses rather than serve gay couples is being sued.

The American Civil Liberties Union (ACLU) of Kentucky filed a class action lawsuit against Rowan County Clerk Kim Davis on Thursday.

Plaintiffs in the case are four couples who were refused a license this week from Davis' office. Half of the couples are gay.

Earlier this week, Davis pledged never to issue a marriage license to a gay couple, saying it would be a violation of her Christian beliefs.

“It's a deep-rooted conviction; my conviction won't allow me to do that,” Davis said. “It goes against everything I hold dear, everything sacred in my life.”

Laura Landenwich, an attorney with the ACLU of Kentucky, said in a statement that Davis “cannot pick and choose who she is going to serve, or which duties her office will perform based on her religious beliefs.”