“…This reading does not necessarily render invalid the present American legal pattern which conditions carrying either on the weapon being unconcealed or on the possession of a carry permit. 3 2 What it does imply, however, is very substantial limitations on the arbitrariness with which permit applications have traditionally been handled. At the very least, police agencies are not free either to limit permits to the wealthy, influential, or politically powerful, or to categorically deny them to all persons.…”