Could be a bug, could be the way things are set up but:
I'm playing as the Terrans and have attacked the Drengin to my opposite left and have in fact killed them off - they have no planets, the one starport and a couple of ships left alive have gone white. I know I could go off and kill the Alterians but I'd like to be done with the Drengin first.
It now appears I can't kill them or seize control of them. Obviously no major problem as I can just skirt by them, ignore them if I can't have 'em or kill 'em, but is this a bug?