According to wikipedia [0], ATC in Germany is subject to the Fernmeldegeheimnis [1]. It’s the same law that protects snail mail and other communications. Anyone who wants to even listen to ATC has to be certified [2], and then has to comply with that law.
One major exception is that you can listen to air band from a car if you're doing so in order to be able to retrieve a balloon, glider (sailplane) or other recreational aircraft.
(husband is a glider pilot who makes an "outside landing" every couple of years)
[0] https://de.wikipedia.org/wiki/Flugfunk [1] https://de.wikipedia.org/wiki/Fernmeldegeheimnis [2] https://de.wikipedia.org/wiki/Sprechfunkzeugnis_(Luftfahrt)