Because proving that someone knew that she was selling a product that would be used for illicit purposes is difficult, the federal law apparently sets the bar at "reason to believe." For example, if a customer comes into her store and says, "I need this cold medicine and aluminum foil to do some cooking to feed my jones," a Reasonable Person would know what he means, even if she disclaims having made the connection from "cooking" and "jones" to drug manufacture.
These assumptions of what a Reasonable Person knows, however, may be complicated by language barriers and even by a failure to acquaint oneself with certain aspects of American culture. My mother has lived in the United States for almost 30 years and speaks standard English, but I would be willing to bet that she wouldn't understand the above to be slang about narcotics, instead assuming that "jones" referred to a person and "cooking" to food production.
Assuming that the defendants in these cases have decent defense attorneys, I suspect that prosecutors will need instances like the retailer who specifically told a customer that he would not report him in for buying suspicious quantities of meth-making material, or even just a retailer who had been ordered clearly and unmistakeably to call law enforcement in such cases and failed to do so. A convenience store owner who simply nodded when customers talked about cooking crystal is going to be more difficult to convict, especially if the defense uses expert testimony about the gap between immigrant retailers and black market culture.
UPDATE: A friend e-mailed the story to me, with the message "If I am pissed, you better be pissed too." I wouldn't say that I'm pissed, exactly, because insofar as the general War on Drugs makes sense, law enforcement needs to prevent the sale of products that are going to be used to make drugs. I'm only troubled by the possibility that people who really didn't know what was happening, and who didn't know because of culture gap, are going to prison for their ignorance. (Which turned out to be irrational ignorance, in contrast to the kind of ignorant Will Baude often characterizes himself to be; as one Ms. Patel said, "I think you need all this bad knowledge now if you want to live here.")