Does he have grounds to have a suit now that his orders were revoked?
Having orders revoked only means they are cancelled for the time being. Probably the appropriate thing to do until his case is resolved. The revocation is only temporary. Major Cook is very clear that he is enthusiastic about deploying once Obama can proof his eligibility, so no one can claim Major Cook is using this as a ploy to avoid service.
If he is court martialed for not deploying, he will be entitled to discovery that will include Obama’s long form birth certificate.
He has put Obama, the military and the U.S. District Court in a very difficult position because he is a man of courage.