Not to start a big hoo-haw, but adultery is a capital offense under Noachide law as well. Of course you have to have a valid Noachide court and prove your case according to the Halakhic rules of evidence . . .
The death penalty was rarely if ever enforced in Jewish law. The axiom was that if a Jewish court sentenced one man to death in 60 years it was a ‘murderous’ court.