I often read and heard about burning tokens that were not sold when the ICO project was finished, I also knew that by burning the rest of the token was a strategy so the price of the token didn't fall, but if the DEV and the team didn't burn it was a crime? is there a requirement that the remaining unsold tokens must be burned?
no, I think that is the result of the policies of the developer and the ico team.
so there is no element of crime on that basis. but if a smart team will definitely burn unsold tokens.