If your friend pierced a girl who presented an identification card showing that she was an adult but was not, your friend should report this fact to law enforcement so as to protect him/her from any criminal problems or licensing issues in the future.Hopefully your friend keeps photocopies of identification cards or driver's licenses of his or her cutomers as a business practice.Assuming your friend honestly believed that the minor he/she pierced was an adult and there was documentation presented showing such, there should be no legal trouble resulting. However, possible penalties could be a fine of $1,000 or more and/or a supension of his/her license to pierce for up to six months.