Well, I was thinking and I saw a website with this.

To force people who want to register on your board to read the rules, I think you should be able to put a code in it randomly so they don't see it at first glance, and once you click 'I agree' it asks for the password/code. Maybe like this:

Please take a moment to review these rules detailed below. If you agree with them and wish to proceed with the registration, simply click the "Register" button below. To cancel this registration, simply hit the 'back' button on your browser.

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Please and thanks,

Jak Easter

This is not the sort of thing a professional site would want to do in my opinion and therefore should be a modification. :)