There are explicit supersonic-permitted areas used by military, but you can actually do supersonic flight as civilian too if you arrange their use (mainly a thing of scheduling so you don't collide with military/state aircraft).
The big rarity of that is that there are very low numbers of supersonic planes in civilian hands, and outside of Concorde and some Tu-144 models (not all of them), all are ridiculous fuel guzzlers in supersonic flight. I know there's one near Palo Alto, a civilian owned MiG-21.
Well, there's one guy in Palo Alto who had instructor permit on it even, and was looking for partner in its ownership (quite common solution for more expensive planes in civilian hands).
The big rarity of that is that there are very low numbers of supersonic planes in civilian hands, and outside of Concorde and some Tu-144 models (not all of them), all are ridiculous fuel guzzlers in supersonic flight. I know there's one near Palo Alto, a civilian owned MiG-21.