I don't think there is any completely fool-proof method.  First, even if
they "agree" to your (new) methodology, they can still lie, cheat, and
steal (your time).  My suggestion would be based more on the particulars
rather than what you  have posted.  My suggetion might be as simple as:

* SUBSCRIPTION= OPEN,CONFIRM
* SEND= EDITOR
* EDITOR= your_e-mail_address,(listname)
* DEFAULT-OPTIONS= REVIEW

Once new subscribers post in-accordance with your agreement, I'd set them
to NOREVIEW.  If they then have a change of heart, set them back to REVIEW.

I'm sure Ben Parker will (or has previously in these discussions) given
insights into how to construct appropriate Template forms.

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