I noticed this interesting case from New York several days ago, reported on Patty Salkins' Law of the Land blog. The case involves an argument by a quarry owner that the quarry was legally nonconforming, and as a result it could continue after a change in the zoning regulations. Unfortunately for the quarry owner, the New York Court concluded that the quarrying operation had never begun before the change in the zoning regulations. As a result there is no nonconforming use. Take a look at the case: Cobleskill Stone Products v Town of Skoharie, 2012 WL 1948307 (App. Dept. 2012).
I was involved in a similar case 10 or 15 years ago, Dickson County v Jennette, 2000 WL 1121550 (Tenn.Ct.App. 2000). Even given the statutory protection found here in Tennessee at TCA §13-7-208, the nonconforming use must have begun operations before the change in the zoning regulations. In the Janette case, just as in Cobleskill, quarrying operations had not begun before the change in zoning took place. You just can't have a nonconforming use, unless the use has actually begun operations before the change in the zoning regulations takes place.