US uses Common Law as derived from the UK's Common Law. In theory in both countries something has to be specifically forbidden.
In practice that's not something I'd bet my not-being-in-jail on in either country. Whatever foundation of "anything not forbidden is permitted" has been crusted up with so many layers of governmental power grab that whatever the theory may be, the practice is that if it is not explicitly permitted it is forbidden, and the only reason things not explicitly permitted are allowed is because they just don't happen to make a fuss about it today.
In practice that's not something I'd bet my not-being-in-jail on in either country. Whatever foundation of "anything not forbidden is permitted" has been crusted up with so many layers of governmental power grab that whatever the theory may be, the practice is that if it is not explicitly permitted it is forbidden, and the only reason things not explicitly permitted are allowed is because they just don't happen to make a fuss about it today.