In early 2008, just eight days before he was to deploy in support of the war in Afghanistan, Lt. Col. Victor Fehrenbach, a decorated Air Force flight officer, was told he was under investigation on charges of sexually assaulting a civilian and of violating the military’s ban on homosexuality.

He was placed on desk duty at Mountain Home Air Force Base in Idaho. Within three weeks, the sexual assault allegation was dismissed for lack of evidence. But the Air Force investigation into his sexuality continued. Now, just a year from completing his 20th year in the military, Fehrenbach, 40, believes he is about to be discharged under the policy known as "don’t ask, don’t tell." He would be among the highest-ranking service members discharged under the policy.

On Wednesday, Fehrenbach’s lawyers filed papers in Idaho federal court requesting a temporary order blocking his discharge. The petition contends that a discharge would violate Fehrenbach’s rights, cause him irreparable harm and fail to meet standards established in a 2008 federal court ruling on don’t ask, don’t tell.

For advocates of abolishing the ban against gay men, lesbians and bisexuals serving openly, Fehrenbach’s case has become something of a line in the sand. Although President Barack Obama has called for ending the ban and Congress has begun moving in that direction, gay service members continue to face investigations and discharge, albeit at a lower rate than in past years.

Lawyers for Fehrenbach assert that his case is among the most egregious applications of the policy in their experience. The Air Force investigation into his sexuality began with a complaint from a civilian that was eventually dismissed by the Idaho police and the local prosecutor as unfounded, according to court papers. Fehrenbach has never publicly said that he is gay.

However, during an interview with an Idaho law enforcement official, he acknowledged having consensual sex with his accuser. Fehrenbach’s lawyers say he did not realize Air Force investigators were observing that interview; his admission led the Air Force to open its "don’t ask" investigation.

Under new regulations issued by Defense Secretary Robert M. Gates this year, "don’t ask" investigations must be based on information from credible sources. Fehrenbach’s lawyers argue that the credibility of his accuser is clearly undermined by the dismissal of the sexual assault case.

His lawyers also assert that his case underscores the ways the ban hurts military readiness, the very thing it is supposed to protect. They say that Fehrenbach’s performance reviews were consistently glowing, including his most recent one, which says he was a "proven leader" who "raised morale" in his unit, according to papers filed by his lawyers.

"The evidence is that he is a benefit to the Air Force and to his unit," said M. Andrew Woodmansee, a San Diego-based lawyer who is serving as co-counsel for Fehrenbach, along with the Servicemembers Legal Defense Network, a nonprofit group representing gays in the military.

An Air Force spokesman, Capt. Derek White, said that Fehrenbach’s case was under final review by the Air Force secretary, Michael B. Donley, and that until a final decision was reached, the Air Force would have no comment.

Lawyers for Fehrenbach said that if the case had reached the secretary’s desk, it meant that Air Force investigators had recommended the colonel be discharged. They said they decided to seek a temporary restraining order preemptively because they believed that his discharge was imminent.

But White said all cases involving possible violation of the ban must be reviewed by the secretary, whether or not commanding officers have recommended discharge.

Fehrenbach’s case rests heavily on a 2008 ruling by the U.S. Court of Appeals for the Ninth Circuit in which the court ruled that an Air Force major had been improperly discharged. The ruling in the case, Witt vs. Department of the Air Force, said that discharging service members for their sexuality was unconstitutional unless the government showed the discharge was necessary to significantly further an important government interest. The Witt ruling applies only to cases in the Ninth Circuit, which includes Idaho.

During his 19 years in the service, Fehrenbach says, he deployed six times as a weapons systems officer, in charge of finding targets and guiding bombs or missiles. He flew combat missions over Kosovo, Iraq and Afghanistan. "I would love to get back into the cockpit and deploy again," he said.

© 2010 The New York Times Company