Forum rules are often posted/revised as a thread which gets buried after some time. A newbie absolutely have no idea about the prevailing rules/regulations.

Suggestion

1) When a user clicks "Start new subject" then he should see a page which explains the major/current rules/regulations which he has to follow (There may be a link for detailed description). At the end of the page, if he clicks "I accept" button, then he/she might be able to post a new subject.

2) This rule can be by passed in case of the users who have seen this page (as the registration is mandatory now, so database can store which user has reviewed/seen that page and set a flag)

3) If that page gets modifed, the database can reset all the flags again to make sure that everyone now again reads them before posting a new subject.

4) On the main page, there should always be a link/button for detailed rules/regulations/ettiquetes etc.

I hope this can further prevent annoying posts, help reduce SMS and so on.