He'd open himself up to harrassment charges. Imagine if cops arrested people because they bought Region 1 DVDs from Amazon or Take2.
Of course by reasonable suspicion what is meant is the sale of drugs, assault, rape, murder, burglary, robbery, etc. Selling illicit copyright works is not something one can eyeball and have a 'reasonable suspicion' about. For one, he'd have to watch the DVD to see if it really contains Pirates of the Caribbean, then he'd have to confirm that it really is a pirate copy and not a different region/alternative publisher release. I'm sure smart a-ses on the forum will say that's possible but there's no way a police officer in a squad car would be able to do that. These guys aren't investigators.
What happens is that SAFACT/BSA/RISA and other shill MAFIAA organisations direct the cops to the bigger players hopefully with magistrate issued warrants. SAFACT/etc are not law enforcement organisations like SAPS, Interpol or FBI they are industry protection bodies and they need the cops to execute arrests/etc on their behalf - with warrants and all.