Christians are invoking religious freedom as a response to the US Supreme Court ruling that legalised same-sex marriage in the US.

In Decatur, Tennessee, employees of the country clerk's office all resigned in order for them not to issue same-sex marriage license.

In Oregon, the owner of Sweetcakes by Melissa bakery is fighting back and urged Christians to take a stand after the couple who owns the bakery was found liable for refusing to make a wedding cake for a lesbian couple.

In Rowan, Kentucky, a county clerk has been sued for refusing to issue marriage license to gay and straight couples, citing "religious concerns."

The American Civil Liberties Union (ACLU) of Kentucky filed the lawsuit on Thursday on behalf of two gay couples and two straight couples against County Clerk Kim Davis.

The plaintiffs in the Kentucky case are same-sex couples April Miller and Karen Ann Roberts, and Aaron Skaggs and Barry Spartman, and straight couples Shantel Burke and Stephen Napier, and Jody Fernandez and Kevin Holloway.

Davis has refused to issue marriage license to any couple.

In Tennessee, clerk Gwen Pope and employees Sharon Bell and Mickey Butler have resigned from their jobs because of the Supreme Court decision and their last day will be on July 14, according to a report by WBIR.

"It's for the glory of God. He's going to get all the glory," Pope said of her decision to resign.

Decatur resident Scott King praised the three women for fighting for their religious beliefs.

"These three ladies stood upon their beliefs and they stood upon their morals and no one can fault them. Too often we as Christians don't do that. It's time we followed the lead of what they showed us," he said.

In Oregon, Aaron and Melissa Klein, owners of Sweetcakes by Melissa, were ordered by the state's Bureau of Labor and Industries (BOLI) to pay $135,000 for discrimination after they refused to make a wedding cake for lesbian couple Rachel Cryer-Bowman and Laurel Bowman-Cryer in 2013.

Aaron denounced the ruling and said he's not backing down.

"For years, we've heard same-sex marriage will not affect anybody. I'm here firsthand to tell everyone in America that it has already impacted people. Christians, get ready to take a stand. Get ready for civil disobedience," he told The Blaze.

He said they will request a stay in the order and will likely appeal the ruling.