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, Colonel 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, Colonel Fehrenbach’s lawyers filed papers in Idaho federal court requesting a temporary order blocking his discharge. The petition contends that a discharge would violate Colonel 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, Colonel Fehrenbach’s case has become something of a line in the sand. Though President 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.