One of the early rockers (Chuck Berry I believe) used to hit groupies all the time. He had a couple of strict rules though: (1) she had to prove she was 18, and (2) before they enjoyed each other's company, he would have them disrobe completely. Then, he'd have one of his roadies snap a picture of the two of them, with her arms around him and a big smile on her face.
This is why he never had to deal with any legal complications.
Maybe Chuck started this AFTER he was charged under the Mann Act.