The last WWII war criminal?

A man who is claimed to be a Nazi guard has been in and out of custody lately in the US.  He is 89 years old and appears to be in pretty poor health.  This is a complete waste of resources.  I don't know what is accomplished by putting an elderly man in jail, and possibly sending him to a country he hasn't lived in in decades.  Especially when he was tried in Israel, but the conviction was overturned.  

With the justice systems' limited resources, we need to focus on people who are current threats; not those who may have committed crimes 65 years ago.