Comment by the_sleaze_

Yes - although I disagree on one point.

All we need to do is define the $thing and mandate that lawsuits can be effective.

No agency enforces that potato chips need to fill up 92% of the bag or whatever, or that McDonalds cannot show pictures of apple fritters with more apples than they actually come with (this happened).

You just incentivize a cottage industry of legal that can squeeze a profit out of suing peanut butter companies for labelling incorrectly, or advertising dishonestly and it sort of takes care of itself.