Spotswood Sansom & Sansbury LLC filed amicus curiae briefs with the United States Supreme Court on behalf of a nationwide association of air carriers to vindicate an issue of great significance to both motor and air carriers—federal preemption of state laws relating to carriers’ prices, routes, and services. The firm filed briefs at both the certiorari and merits stages to support trucking companies that challenged various requirements imposed by the Port of Los Angeles, California on federal preemption grounds. The city argued that the requirements were saved from preemption because it was acting in its capacity as a market participant, but the Supreme Court rejected that argument and agreed with positions advocated by Spotswood Sansom & Sansbury.