Robbo, I can't see any harm in unbanning him from this site, maybe with a caveat that any deals he does in buy / sell are through a thrustworthy third party or he's just plain banned from posting there. He'll probably end up as a pariah for his passed actions on here anyway, maybe in a couple of years the community will forgive, but I doubt anyone will ever forget.
As for the rest of the paintball world that'll be up for the individual event organisers to decide anyway won't it? you obviously can't tell them to forget everything you told them about him, I'm assuming you didn't tell them to ban him in the first place, you just advised them what had happened and they made their own decisions, so unless you lied and said "I was wrong about him, he never did that" they are unlikely to welcome him back with open arms.
As for the rest of the paintball world that'll be up for the individual event organisers to decide anyway won't it? you obviously can't tell them to forget everything you told them about him, I'm assuming you didn't tell them to ban him in the first place, you just advised them what had happened and they made their own decisions, so unless you lied and said "I was wrong about him, he never did that" they are unlikely to welcome him back with open arms.