U.S. derivatives professionals are concerned the National Association of Insurance Commissioners' recent ruling that weather derivatives should be classified and regulated as insurance, rather than a capital markets product, could shut broker/dealers out of the market. If the conclusion is accepted by U.S. state regulators, as NAIC rulings typically are, weather derivatives could become the exclusive preserve of insurers, according to lawyers. Roger Hoadley, spokesman at the NAIC in Kansas City, Mo., did not return calls.