Because we were getting a few people that signup to the forum and go straight into chat who haven't read the rules and act badly we started hiding the chat link to people with under 3 posts. I have since changed this to 1 post and we are discussing the situation within the moderators forum to figure something out that is permanent.
Perhaps the rules could be the first port of call and chat access allowed only after the user confirms they agree to abide by the rules. The multi-post restriction is a good idea too. Any breach of the rules and it's back to square one.