I don't know how the law works in the US, but isn't the selling by C illegal and moot? C accepted the conditions, but did not repect them.

Shouldn't C be attacked (legally of course) automatically?

Say C decides to build on a land they own a nuclear plant with known life endengering issues. Or a place to publicly hang people. Or other completely illegal things. They will surely be stopped by someone (the state?) from doing this? Automatically, that is without the need for a citizen to raise the point.

This is a similar case: they want to do something illegal (not follow what they ageed to)