Depends on the place. Some places will just do it outright, we prefer to give people a couple of chances. Edit to add: But it's not like there's a law on it; people who start up a forum can ban whoever they want whenever they want.
exactly what daftscotslass said, the people who make it make the rules. I was banned from one forum because I was a moderator on another... no warning... not against their rules but banned all the same. Look at it this way hun... its their loss
I once had my posting priveledges and pm taken away from me on a forum for joining up apparently (I didn't) as other people and pming them, only problem was I was on holiday at the time and didn't even have access to the internet and I'm not that stupid. Never believed it wasn't me even though I wasn't even around at the time :S I was having a lovely holiday at the time and was most confused when I got home. I don't play games. It's not a forum around these days. But I was cross, I didn't even do anything as I don't do that sort of thing rolleyes