My friend is a bad father. How do I get him to leave his daughter alone?

He never lets his daughter (17) go anywhere. He treats her like an 11 year old. His daughter recently lied to him, in order to go to a sixth form party. I know this because my son goes to the same school and he went too. It was a bit of harmless fun. He claims that because there was alcohol on the premises, it was not a suitable establishmshent for a 17 year old girl to be. I totally understand his view point, but she doesn