A photographer opposed to same-sex marriage has filed a lawsuit challenging Louisville, Kentucky's Fairness Ordinance, a 20-year-old law that prohibits discrimination based on several characteristics including sexual orientation and gender identity.

Chelsey Nelson, the owner of Chelsey Nelson Photography, is represented by the Christian conservative Alliance Defending Freedom (ADF).

Nelson claims that the ordinance is forcing her to participate in same-sex wedding ceremonies that she disagrees with.

The city is using “the threat of limitless damages” to force Nelson to “create photographs for, blog about, and participate in solemn ceremonies she disagrees with – same-sex wedding ceremonies,” the lawsuit states.

“For Chelsey, the choice is simple yet stark – violate the law, forsake her faith, or close her business,” the suit adds. “These options are unacceptable.”

In a USA Today op-ed, Nelson said that while she serves “everyone regardless of who they are,” she can't photograph every wedding request. “For example, I can't celebrate a wedding that devalues how seriously I take marriage – like a heavily themed Halloween or zombie-themed wedding.”

“The government shouldn't force artists to express views they disagree with,” she added.

Defendants named in the lawsuit include Louisville Metro Government and Louisville Metro Human Relations Commission Enforcement.

Nelson's ADF lawyers said that she has not been asked by a same-sex couple to photograph their wedding.

Chris Hartman, director of the Fairness Campaign, a Kentucky LGBT advocacy group, called the lawsuit “ludicrous.”

“This has been an instrumental part of civil rights laws since the Civil Rights Act passed in 1964," Hartman said.

"And so to challenge it today, nearly 60 years after the Civil Rights Act passed, and 20 years after the Fairness Ordinance passed, is ludicrous and speaks to how low the Alliance Defending Freedom is willing to go to undermine LGBTQ civil rights and in fact, civil rights for all people,” he said.