The equivalent right in the military is to plead Article 31 of
the UCMJ.
Captain's Mast is not a court proceeding, it is nonjudicial
punishment. One of the advantages of a Captain's Mast is that while
it does have a negative affect on your military career, it is not
something that records as a criminal trial. You can refuse
Captain's Mast and request a Special Court Martial.