Shouldn't Unilateral Retroactive Copyright Extension Mean Copyright Is Void?

With Europe approving this ridiculous retroactive copyright extension, which has set off an angry public who is reasonably frustrated that they'll be paying the cost to support a few rockstars and dying record labels -- there's an argument that this fundamentally breaks copyright law. And, it's making me wonder if it actually should mean that copyright is null and void. I've argued in the past...