Add a new rule called “Involuntary Changes Treaty” and give it the following text

If a contents of a treaty are changed by a proposal, and a signatory of that treaty who is not the Player cast an AGAINST vote on that proposal, then within 48 hours of the proposal being enacted the signatory in question may make a post to the blog announcing their disagreement. Upon doing so, they cease to be a signatory of the treaty in question.

After doing so, they may not voluntarily become a signatory of the treaty again, expect if enacting a proposal would make them a signatory. Furthermore, if they do become a signatory again, they retain any game state values they had for that treaty prior to the point where they ceased to be a signatory.