Standing is the legal right to initiate a civil lawsuit. This is a criminal trial. If Lakin is convicted then his right to appeal his conviction is guaranteed.
This is a Court Martial so his appeal is automatic, the case will be reviewed up the chain of command, and it cannot be appealed through civilian courts.
By denying his right to ask for Obama's eligibility, at least a reviewing authority will be forced to set aside a conviction and order that the Court Martial be expunged from his records as a nonevent based upon his rights to a fair trial being denied to him.