When Kerry gave his "war crimes" testimony before Congress, and also when he met with the Viet Cong and North Vietnamese representatives in Paris, he was NOT a civilian. However inactive his service status was, he was still enlisted in the US Navy as his commitment was not completed. So his actions in those two instances WERE subject to the UCMJ.
Congressman Billybob
Latest column, "Mein Fuhrer, I Can Valk!"