We shouldnt get too emotional and violate the treaty aspect of it. If we can put him in a max security prison with zero communication, he is as good as dead.
If we violate any of this treaty we may never get other criminals extradited successfully. Its more important to control crime than to put criminals to death. There might be tons of information than salem may have that may enable the crime world to crumble. Frankly hes a good catch.