Johnathon Adler at the Volokh Conspiracy supports an argument that maintaining the Don’t Ask, Don’t Tell policy has no legal basis in light of the statements of top military officials that ending the policy will not affect unit cohesion.
The courts are — and should be — quite deferential to the military’s own assessments about what sorts of rules are necessary to maintain a well-functioning military. But if the military’s leadership does not believe that a policy of excluding open homosexuals serves this purpose, I see little reason for courts to defer to a contrary legislative conclusion.
Adler points to this Washington Post article that outlines the argument in more detail. Both are worth the read.