I don't think there are hard rules for when it can or can't be used, but it's worth noting that bans are almost universally applicable when it comes to applying broad regional descriptors to specific ethnic applications. So, calling a Persian rug "oriental" would also be problematic, particularly if one were to ask such a thing of a dealer who sells antique rugs. Furthermore, applying any kind of regional marker, even one that is specific, can either be offensive or not depending on the individual. Because the term "oriental" is not derived from an specifically racist origin, it's hard to say that the use of the word is racist outside of a specific context that entails its own racism (such as say, the use of "oriental" in a WWII era depiction of Japanese in comics).