Specifying that it is a misdemeanor punishable by imprisonment for up to 5 years or a fine of up to $10,000 or both to knowingly violate the prohibition against the possession of a regulated firearm or ammunition solely designed for a regulated firearm by a person who is under the age of 21, or to knowingly violate the prohibition against obliterating, removing, changing, or altering the manufacturer's identification mark or number on a firearm.