You can stop certain I.P's from posting new threads on certain club forums I believe though David.
The problem with that is that most ISPs don't provide you with a static IP unless you pay for it (usually only people who want to play games on-line pay for static IPs). If you don't use a static IP and a forum moderator bans one IP that won't stop posts when the IP address changes. If a moderator bans a range of IPs, that includes all the other visitors who use the same ISP.
See Cyclops, I told you you were an anorak!!!