Growing up my father believed playing the GTA would be detrimental to my development. He banned them from our home and told the parents of my friends not to let me play those games at their house, if they said they wouldn't enforce that rule I wasn't allowed over.

Didn't matter, I played the games to completion at friend's houses because their parents didn't really give a crap.

Looking back, I think the only way my father could have reasonably stopped me from playing these games would have been to isolate me from my friends and wreck our relationship. Now luckily, we're pretty sure no harm was done in this case, but the point is that there's not actually that much parents can do to limit access to content if other parents aren't similarly vigilant.