Public Advocate of the United States, a conservative nonprofit organization led by Loudoun County Supervisor Eugene A. Delgaudio (R-Sterling), filed a motion Friday to dismiss a federal complaint alleging that the organization illegally used a same-sex couple’s engagement photo on anti-gay-marriage campaign fliers in Colorado.

The Southern Poverty Law Center, a prominent civil rights organization that designated Public Advocate as a hate group this year, filed the complaint in September in U.S. District Court in Colorado. The SPLC is representing Tom Privitere and Brian Edwards — a New Jersey couple pictured on the campaign mailers sent out by Public Advocate in June — and Kristina Hill, the photographer who copyrighted the image.

The original photograph, taken by Hill in 2010 and posted on Privitere and Edwards’s wedding blog, shows the couple kissing in front of the New York skyline. In one of two altered images featured on the widely distributed Public Advocate campaign flier, the city backdrop is replaced by a country setting, and a bright red banner with the words “State Senator Jean White’s Idea of Family Values?” cuts across the couple’s chests.

The lawsuit alleges that Public Advocate’s use of the image was in violation of federal copyright law. It also says that the group did not have permission to use Privitere and Edwards’s likenesses and that the unauthorized use of their photograph resulted in emotional trauma and threats against the couple.

Public Advocate, represented by the Arrington Law Firm in Centennial, Colo., said that the use of the couple’s photograph was fair and protected by the First Amendment.

“This case is about one and only one thing: the politics of same-sex unions,” the memorandum stated.

Because the plaintiffs acknowledged that Public Advocate used the photograph to express its view on the issue of same-sex unions, “this admission is fatal to their case,” the memorandum said. “Public Advocate was engaging in the type of political speech the protection of which is at the very core of the freedom of speech guaranteed by the First Amendment.”

Public Advocate also says that the plaintiffs could not have had a reasonable expectation of privacy, because the photograph was posted on a blog where “anyone in the world with access to a computer could view it.”

Privitere, Edwards and Hill have said that the alterations to the original image — the changed background and the bold red slash across the couple’s chests — were especially disturbing. Public Advocate maintained in its court filing that those changes were, in part, what justified “fair use” of the photograph.

“Public Advocate used only the images of the two individuals from the photo and thoroughly transformed the photo by the addition of an entirely different background which removes the big city feel and places the individuals in a country setting consistent with the message and voter education purposes of the mailers,” the memorandum says

Public Advocate, which regularly raises more than $1 million annually, according to IRS records, has a long history of controversial mass-mailings, including one widely distributed e-mail last year that showed a murder scene with blood stains in the color of a rainbow, a symbol of the gay, lesbian, bisexual and transgender community.

As the organization’s longtime leader, Delgaudio has been open about his position on gay rights and same-sex unions. He has claimed that airport pat-down procedures, anti-bullying legislation and a popular Florida pirate festival demonstrate the growing influence of “radical homosexuality.” Such statements have repeatedly drawn the condemnation of Northern Virginia Democrats and groups that promote equality.

Delgaudio did not respond to a request for comment Monday.

The veteran Loudoun supervisor has been under fire in recent weeks after a report in The Washington Post in September that detailed allegations by a former aide who claimed that she spent the majority of her working hours earlier in the year making phone calls to schedule fundraising meetings to benefit Delgaudio’s political campaign.

Delgaudio has repeatedly denied the accusations and said that his fundraising efforts were solely to benefit a local youth football league. Loudoun policy prohibits engaging political activity on county time or using county resources.

Loudoun retained National Consulting and Investigating Services, an Ashburn-based firm, to conduct an independent investigation of the allegations against Delgaudio. The county Board of Supervisors voted unanimously Oct. 3 to pursue the review and budgeted $15,000 for the investigation.

Dan Wright, president of National Consulting and Investigating Services, is a former FBI agent, according to his résumé. Wright is expected to work with Amy Hutchens, an attorney with Watermark Risk Management International who specializes in corporate compliance and ethics, according to an engagement letter from County Attorney John R. Roberts.

The investigation will begin this week, and a final report is expected to be delivered within 60 to 90 days, the letter said.

The Real Advocate political action committee, led by former Loudoun supervisor Stevens Miller, questioned whether the choice of a local investigative firm presented a conflict of interest. A Loudoun-based company “is subject to regulation, taxation and investigation by the very government it is being asked to audit,” the committee said in a statement Friday.

Loudoun County spokeswoman Anna Nissinen said that the firm was hired “solely based on their professional qualifications.”