Helen wrote about the Federation administration:
They fear political crimes so much they would rather covertly slaughter large groups than try to brainwash them.This from a society that appears to have no official death penalty (I may be wrong).
Two possible exceptions:
(1) Glynd, Morag and Havant discuss eliminating Blake rather than deporting him. The dialogue runs as below and one interpretation might suggest trial and execution for dissidence, though possibly a more likely one is another 'transporter accident'.
HAVANT Can't he be eliminated? MORAG No, he's a symbol of opposition to the Administration. ... MORAG His death could be used by the dissidents. They need a hero. Alive or dead, Blake could be it. HAVANT Difficult. I suppose my department could infect him, some rapidly terminal disease. Would his natural death help? GLYND I don't think so. MORAG What we need is something to discredit him. If he could be deported to Cygnus Alpha ....
(2) Travis is sentenced to execution in a Federation military court in Trial. Not only would I argue that this counts as the death penalty existing under Federation law, but the wording of the sentence suggests that some non-military criminals were executed.
SAMOR We cannot find it in our hearts to absolve you in any way of the responsibility for these murders. The sentence of this tribunal is, therefore, that you should be stripped of all rank and privileges, that you be dishonorably dismissed the service, and that you then be executed for the common criminal you have shown yourself to be. Have you anything to say?
Tavia