Not much they can do IMO. Sure they can police it, but on most aircraft, part of the overhead bins over row 1 are taken up by safety/FA equipment. That already gets rid of some space. Then theres space for about 2-3 bags for the 4 people in row 1, not including the personal items that also need to fit somewhere. I've recently only been sitting in row 1 as I prefer the bulkhead, and I always make sure I'm first in line to board so I find space. Even then, with GS boarding before, etc, I still have to put one of my items above row 2. Not the end of the world, but it is a negative about row 1.