I don't know what the law is in Mexico and Canada, but I happen to know that in Denmark a boxers fists are considered a deadly weapon, even on registered amateur boxers.Can be considered attempted homicide....
Professional boxers do not have to register their hands as lethal weapons. There isn't any governing body or law that requires it. But the hands of a boxer could be considered a deadly weapon in a court of law if they are used to inflict serious harm
They throw the book at boxers who gets into fights outside of the ring.