Except that they don't. If I walk around a conference saying that all the women at this event are filthy whores who should go back to the kitchen, what law am I breaking? Do you really think that's acceptable behavior at a conference?
My feeling is that codes of conduct mainly serve the salesmen and workshop providers. The thankfully defunct Ada Initiative was the worst actor, but others have stepped in.
http://geekfeminism.wikia.com/wiki/Conference_anti-harassmen... - here is a very reasonable CoC that mostly deal with behavior that is actually law breaking.
Someone actually flagged my comment, which to me is pretty jaw dropping. This isn't a topic we can discuss? Okay.