Someone tried to make a rule that all guides must be verified, but we abandoned the idea quickly. As is, we've removed even the voluntary verification system because of its numerous flaws: not enough mods willing/able to manage it, no system in place to lock outdated guides, restricted ability of mods to communicate which users are selling which methods (resulting in ripped guides getting verified), mods approving shit guides anyway, etc.
I would like to monitor guide sales, but there's really no practical way of doing so at this point. As for removing guide sales entirely, there's too much demand for gp transferring guides - as a Runescape blackmarket, we can't really tell users they can't sell them.