Really good end-of-year piece by Laura Gilbert at Artsy. Not all five are "cases," but I especially liked her take on the proposed authentication legislation in New York:
"THE TAKEAWAY:
If the bill passes in its present form, authenticators still face the risk of paying their own legal fees, even if they win, which is what sidelined them to begin with. Whether the possibility that a losing plaintiff will have to pay their fees will provide enough reassurance for authenticators to once again re-enter the market remains to be seen."
Also good (but not quite as legal-focused): Georgina Adam in The Art Newspaper: 2015's biggest art market developments and what they mean.
