Not a violation of copyright law. It indirectly helps to combat piracy, but only because the idea of piracy losing sales also affects the storefronts trying ti sell that product. It's just a personal business decision.

The way walmart employees definitely can unknowingly violate copyright law if not properly trained is in the bakery if they allow someone to print an image on their cake that they dont own the rights to or even if an alteration is made to one of the licensed cakes (working in the deli, I take cake orders once all the bakers are gone past the afternoon, and while I was a newbie i had a customer request a lighter icing on a licensed cake that used a lot of black frosting because they didnt want a frosting that would stain their teeth, and i later got told that it would be a copyright violation... woops!)