"The current implementation of CDS will prevent you from scanning in banknotes [...]"
Ah..... THAT may be the case. I didn't use a TWAIN image acquisition. I run BetaScan on my old Mustek SCSI scanner. Certainly there is nothing in Photoshop that stops you from opening certain images based on image content.
I bet current TWAIN drivers tag images as "restricted" when they encounter certain moire patterns (patterns used to intentionally disrupt copiers).
Photoshop then respects the "restricted" tag, and refuses to open the image. So, photoshop isn't making a judgement on the image, it is just respecting the "restricted" flag, which shouldn't be set, unless the image had a certain pattern in it when it was scanned.
That would be a way to get that sort of thing into computers without much fuss or hassle. And, under current laws, I believe it would be illegal to remove the moire detecting code from scanners/drivers, just as it is illegal to remove it from modern copiers.
I should try this on my mum's new HP scanner and see what happens.