Stopping proxy access?

Is there anyway I can stop people accessing my forum using a proxy?

Not really.

yeah, theres no real way. Proxy's block/change the IP Adress of the user, so your best bet is to email ban?

But, then they will still come back.
Just keep banning. It'll get you "members".

Hm, just annoying because I'm trying to stop a previously banned member from rejoining. He was banned for going against the forum rules and harassing my members to join his site instead, and he sends PM's so I can't catch him.

Just keep banning him till he gets bored & leaves.

I don't think he's going to give up that easy, plus I'm having a hard time catching him when he rejoins because he used different proxies and email addresses every time.
He's stealing the content from my site for use on his site also

I don't think there is a foolproof method to stop this. Maybe, stop new users registering for sometime if possible.

I have it set now so that I approve new members. I get an e-mail notifying me and it allows me to activate them manually. That stopped an issue I was having.