(NapaValleyRegister) - A review of how Napa County applies and enforces the 23-year-old Winery Definition Ordinance has created a rift between wine industry groups, and disagreement on how older wineries should show compliance with the ordinance if they seek to expand production. At the heart of the dispute is the rights given to the so-called “grandfathered” wineries — those existing before the county adopted the ordinance in 1990 — and its cornerstone 75-percent rule, which requires new wineries to source their wines from 75 percent Napa grapes.