Hello, I am assuming one cannot just scan these pictures from books and print them to sell commercially as this would obviously be an infringement of copyright law, so do people like this have permission to do so?
There is one way that permission could be accounted for. Ken has licensed Transatlantic Designs to sell prints of his work. So if someone has bought from them and later decides to dispose of their print they would be dealing in something that had been legitimately obtained and that they had the single copy ownership right to dispose of. The key thing would be to feel assured that this is was indeed a one off official print and not a quick scan for multiple sale. Asking the seller about buying more copies could be an easy test, although he could also just be ordering and reselling Transatlantic’s while hoping to lure you into a higher price with mistaken thoughts of rarity. For the case at hand comparing “6x8 digitally generated” with authentic offers on Transatlantic’s site just doesn’t pass muster however.