"In one Georgia case, authorities made mass arrests of immigrant store clerks and owners, but it's starting to look less like a criminal conspiracy and more like culturally naive foreign-born merchants simply trying to sell their merchandise."
Ignorance of the law is no excuse.
Past time to change the law.
It's not illegal, per se, to sell cold medicine, antifreeze and aluminum foil.
Heck, I buy cold medicine, antifreeze and aluminum foil several times a year (maybe only once or twice a year for antifreeze).
That's not what's against the law.
I gather that what's against the law is selling it to drug dealers -- how on earth can you know what the purchaser intends to do with these items?