A same-sex couple whose engagement photo was allegedly stolen and widely distributed on anti-gay campaign mailers in Colorado has filed a federal lawsuit against Public Advocate of the United States, a conservative nonprofit organization led by Loudoun County (Virginia) Supervisor Eugene Delgaudio.

The Southern Poverty Law Center, a prominent civil rights group, filed the complaint Wednesday in U.S. District Court in Colorado on behalf of Tom Privitere and Brian Edwards, the couple pictured on the campaign fliers sent out by Public Advocate in June, and Kristina Hill, the photographer who made the original image.

The lawsuit seeks unspecified damages for Public Advocate's alleged copyright violation and the use of Privitere and Edwards' likenesses without permission. It also describes the "mental distress and anguish" that the couple has suffered as a result of the alleged theft and misuse of the photograph.

The lawsuit follows a public outcry after news of the campaign mailers first became public in July — the most recent controversy involving Public Advocate, which was designated a hate group by the SPLC earlier this year. The organization, led by Delgaudio (R-Sterling, Va.) since 1981, has a long history of controversial mass mailings, publications and street theater aimed at protesting what Delgaudio calls a "radical homosexual" agenda.

Asked about the pending lawsuit Tuesday, Delgaudio said by email, "I'm looking into that." He declined to comment further and did not respond to for a request for comment Wednesday.

Of more than 1,000 organizations in the United States that are designated as hate groups by the SPLC, Public Advocate is the only one believed to be led by an elected public official, according to officials with the civil rights group.

Christine Sun, deputy legal director for the SPLC, spoke publicly outside the federal courthouse in Denver after the complaint was filed Wednesday morning.

"Our clients have been devastated by this heinous misappropriation of what once reflected a beautiful moment," she said, according to a prepared statement. "We hope this lawsuit sends the strong message that hate groups may only promote their ideologies within the parameters of the law, and that they must answer for their actions when they do not."

The original photograph, taken by Hill in 2010, showed the couple kissing before the New York City skyline. In one altered image distributed by Public Advocate, snow-covered pine trees replaced the city setting, and a bright red banner with the words "State Senator Jean White's Idea of Family Values?" cut across the couple's chests.

The mailer targeted Colorado state Sen. Jean White, a Republican who has voted in support of a bill to allow same-sex couples to form civil unions. A doctored image was also used on another, similar mailer criticizing Jeffrey Hare, then a Republican candidate for the Colorado House of Representatives.

"That red slash demonstrates the hate that some have towards our community, and it speaks volumes," Edwards said Wednesday, according to a prepared statement. "And that is why we are here today, to take back our personal image and to take a stand against such vile and disgusting actions."

According to the lawsuit, Edwards and Privitere have feared for their safety because of the incident and the resulting publicity.

"Edwards and Privitere have been targets of hate messages by people who have seen their likenesses" on the mailers, the complaint said. "People have posted on the Internet that Edwards and Privitere deserve to go to hell, that they deserve to be killed, and that any children that they may have would be better off dead."

In a previous interview, Edwards said that the experience was a powerful echo of dark moments from his youth, when he said he was frequently bullied for being gay.

"I was one of those kids who was called [an anti-gay slur] every day. I was one of those kids who had his car vandalized and got beat up," he said. "And then out of nowhere comes this," he said of the mailers. "It immediately felt like bullying again."

In the same interview, Privitere said that seeing Public Advocate's statement emblazoned across the couple's favorite engagement photo felt especially personal.

"It's hatred directed at us," he said. "And quite frankly, you know, we're just a normal, average, loving couple that goes to work and goes home. We're no different than the person next door."