A dishonorable discharge requires courts martial, and usually involves criminal activity or something serious like giving secrets to the enemy, sabotage, etc. These days, even AWOL (or UA in Navy terms) personnel usually get "other-than-honorable" (but not dishonorable) discharges which is considered administrative separation. Here recently, a Captain in the Coast Guard was convicted of snorting some of the Cocaine he was in charge of seizing. He gets to keep his retirement but will be asked to resign... Legally he is still a veteran.
