1.
Barry Epstein asked:
A court cannot impose capital punishment on a Jew who killed an idolater. Does he just go free?
Barry Epstein, Dallas, USA
2.
The Kollel replies:
I assume you are talking about a Nochri (as mentioned here on 40b). The Minchas Chinuch (Mitzvah 34:1) quotes the Kesef Mishnah as saying such a person indeed goes free, and Hash-m will judge him. Obviously, if Beis Din knows someone intends to do this, they will take all measures to stop him before he does so.
All the best,
Yaakov Montrose