You'll be surprised to hear it, I suspect, but restaurant customers in Communist countries or those under military dictatorships didn't need no stinking First Amendment to scribble on restaurant checks. I have an impression that most people who write about "First Amendment rights" have no idea what it is and what it refers to, but I know for certain that it has nothing to do with restaurant checks and receipts.
Yeah, I know nothing about communism, despite being an area expert on the DPRK (North Korea) and an intelligence analyst dealing with the Soviets, East Germans, etc. Go on, I’m all ears...