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.