The solution is a regulator who buys random goods, thoroughly checks them, then fines Amazon for products found to be unsafe/illegal.

Amazon could then persue the manufacturer for sending bad goods.

Or... Amazon could say "this is a third party seller on our platform, so blame THEM",then the third party seller gets held responsible for the fraudulent goods despite having no ability to control it. Not a very sane system but apparently the one we chose to use (at least until now, when Amazon decides to eliminate commingling).