In summary The California Supreme Court ruled that cities can’t make taxpayers complete extra procedures, handing Marathon Petroleum a win in its tax battle with Carson. California cities can’t require taxpayers to navigate extra local procedures before seeking a tax refund in court, the California Supreme Court ruled Monday in a long-running lawsuit involving Marathon Petroleum, which operates the state’s largest refinery. Marathon operates its Carson and Wilmington refineries as one unit, the Los Angeles Refinery, comprising 27% of the state’s crude oil capacity. The refund question concerned a local tax on refineries that Carson voters approved in November 2017, levying a .25% tax on business conducted within the city. Tesoro calculated the tax based on the business it believed actually took place inside Carson, the company said in its petition to the top court.