The military's ban on openly gay troops will be lifted within weeks, but the policy can still be re-enacted in the future.

That's why a Republican gay rights organization that sued the Obama administration to stop enforcement of the policy says it will ask the 9th U.S. Circuit Court of Appeals on Thursday to declare the nearly 18-year-old law unconstitutional, affirming a lower court's ruling last year.

With several Republican presidential candidates, including Rep. Michele Bachmann, indicating they would favor reinstating the ban if elected, such a ruling is needed, said Dan Woods, the attorney for the Log Cabin Republicans. Declaring the law unconstitutional would also provide a legal path for thousands discharged under the policy to seek reinstatement, back pay or other compensation for having their careers cut short, Woods said.

"The repeal of 'don't ask, don't tell' doesn't say anything about the future," Woods said. "It doesn't (explicitly) say homosexuals can serve. A new Congress or new president could come back and reinstitute it. We need our case to survive so there is a constraint on the government to prevent it from doing this again."

During her campaign stop in Iowa in August, Bachmann told interviewer Candy Crowley on CNN's "State of The Union" when asked whether she would reinstitute the law: "It worked very well and I would be in consultation with our commanders, but I think, yes, I probably would."

Justice Department attorneys have filed a motion asking the appeals court to dismiss the case, arguing that the repeal process that will lift the ban Sept. 20 makes the lawsuit irrelevant.

The Log Cabin Republicans successfully won an injunction by U.S. District Judge Virginia Phillips last year that halted enforcement of "don't ask, don't tell" briefly, before the 9th Circuit reinstated it.