We require a waiver from an external site that must be digitally signed. This could easily be accomplished using the rules and terms field. The problem is the only required entry is to manually check the block that does not require actually clicking the link. I am thinking the fix could be making it so you cannot manually check the block. This would only be checked if the link was followed.

This still will not ensure the waivers are signed, however at least they have to go to the waiver.