You guys are all right !! Believe me, somehow confiscating this guys snakes crossed my mind. Your right, the cops won't care either. If anything they could take them if he didn't have a liscense(need an exotic pet liscense in nj) and having them out in public.
As far as feeding the field mice, it sounded like he lived in a basement of a farm house .
I just tried to get in his head the basic importance of heat and maybe make the lives of these snakes a little bit easier.