Proof laws don't work.
No, it's proof that lawmakers are willing to put exemptions into the law when it benefits them. That's bad, but it doesn't mean laws don't work.
If anything, it indicates the opposite. If laws didn't work, then lawmakers wouldn't have to bother to put exemptions in them.
Well... proof that we can't trust politicians to pass laws that are good for us but bad for them, at any rate.