Surely all this does is makes offshore tax havens all the more attractive? Sure, some of them have signed up (i.e. Panama), but if they are not ditching the territorial taxation system, it changes absolutely nothing for them, and even if it would, Panama absolutely does not care about enforcing the exising law regarding taxation.

Sure, the companies will have to pay a bit more to their lawyers, but the way I see it, is that all it does is making offshores even more attractive.