Southern Pacific Co. v. Arizona Ex Rel. Sullivan, Attorney General

Arizona's Train Limit Law capped trains at fourteen passenger or seventy freight cars, but because other states permitted longer trains, Southern Pacific (plaintiff) had to disassemble its longer interstate trains at the Arizona border and run roughly 30% more trains through the state, substantially increasing operating costs and reducing efficiency; Southern Pacific sued Arizona's Attorney General (defendant), arguing the law unconstitutionally burdened interstate commerce. The trial court agreed, the court of appeals reversed, and Southern Pacific appealed to the Supreme Court.