Wouldn't that break the terms of the treaty? I presume that breaking the treaty either has a direct penalty or you're just kicked out entirely. If you're kicked out entirely, that changes the trade structure that your economy has adapted to over the time the treaty was in place. You'll face serious opposition from businesses that have grown to depend on those new trade arrangements.

Local laws can be adapted piecemeal, but my understanding is that a treaty like this is all or nothing.