You missed the point. Imagine we want to deport a British citizen to Britain for felony fraud committed in US, and it just so happens that the same person is wanted in Britain for a completely different crime, say burglary. We know that if we deport him, he will be jailed and prosecuted in Britain according to British laws. Should this prevent us from deporting him? Is him being considered a criminal in his own country somehow protecting him from deportation there? Are we only allowed to deport non-criminals, and must keep foreign criminals in US, lest they get thrown in jail in the countries we deport them to?