Almost every country has something like that. The Dutch Agentschap Telecom will hunt you down for transmitting a fake GPS signal too.
The thing is, nobody cares if you send a signal too weak to go beyond a meter of your pocket. That's why it's totally legal to send FM on registered frequencies as long as your output is under a certain amount. Same with WiFi even.
I heard about someone looking into GPS spoofing once in the context of catching drones, even nearby ones (e.g. fly near to it). It takes a lot of energy to do that and was basically not practical outside of military settings.
This is not always true - FM transmitters were not legal in the UK, regardless of power, until 2011 or so. Can't imagine anyone was actually prosecuted for using one, though.
If there is no chance of getting caught anyway, there is only moral law. Since you're not disturbing anyone with an FM transmitter in your car that transmits only as far as you car radio, it passes moral law.
Interesting to learn that it wasn't legal in the UK though. I wouldn't know of the legality in the Netherlands, but I know they're in use and nobody's complaining.
