As I said on the other post, the no ones going to tell me what to do brigade and there's a lot of them. What I would do if I were on the tills or management of a store having to deal with those constant difficult customers is, I would point to the CCTV cameras in the store and say "When this is all over, we won't forget your contribution".
Remember the saying "A countries population is 3 square meals away from anarchy". Whilst you have selfish s*ds stockpiling, even though they have plenty of stuff at home, a fair share out system is difficult to police, after all someone who appears to be having more than is needed in their shopping trolley may in fact be shopping for an elderly person or persons as well as themselves, who's to judge?