The USA arrests people who have a business that sells bitcoins without a money transmitter license. https://www.manhattanda.org/d-a-bragg-announces-indictment-in-citywide-illegal-bitcoin-atm-operation/

The name of the crime is "Operating an Unlicensed Money Transmission Business."

The law is here: https://www.law.cornell.edu/uscode/text/18/1960

They define money transmission as "transferring funds on behalf of the public by any and all means." If your business gives people bitcoin in exchange for dollars, the government considers that transferring funds, and they arrest people who do that without a money transmitter license. They're not going to ignore that law just because you wrote the private keys down on a piece of paper first. They will still say your business transferred bitcoin to someone in exchange for dollars and did so without a license and then they will arrest you for it.