A Forum Mod, i got experience in a few sites.
A little story about it...
Long time ago, i was a mod in a forum and a guy found out that he was banned, he was my best friend back then, so he sent me a PM saying "SW, Why am i banned?" i just said: "Sorry bro, you broke the rules, you pay the price" and i gave him proof of it, he was so angry at me, i just said: "Look, rules are rules, i cannot make exceptions just because you're my friend".
I always make that clear from day 1. Obey the rules, if you don't, i'll ban you even if you're my friend/best friend/etc.