This is a law that his been set in place since the creation of the automobile (Well at least since the creation of the Car Radio). The passenger only touches the radio when requested to do so or after requesting permission and receiving approval. There are no exceptions! Violators of this law will at a bare minimum get a severe hand slap and if the passenger continues to break this law will likely end up finding an alternate source for transportation.

When I was teaching my kids to drive I controlled the radio because I couldn't handle their driving and their music at the same time. After their driving improved to a point that I was no longer terrified I turned the radio back over to them but still controlled the volume. I don't like to drive so happily submit control of the radio to the driver.