Bealzebub, I would argue that contrary to your statement, aircraft certified devices such as emergency VHF radios would definitely be covered by Sec. 91.21 (b) 5. Certification implicies "the operator of the aircraft has determined". If not, the aircraft can not fly since the operator has not certified its own aircraft.
Radeng, in case the general public is to be unaware of ATC communications, it would be illegal to sell VHF radio's and scanners to non-licensed individuals.
Amazing to see how the UK went from liberator during WW2* turned into a police state that makes Putin look like a girl scout. In the US, something is allowed until there is a reason not to allow it. In the UK, everybody is a terrorist until proven not to be. You guys even kill innocent subway passengers...
* and yes, Godwin's law applies here.