Bibb, Director, Dept. of Public Safety of Illinois v. Navajo Freight Lines, Inc.

Illinois required commercial trucks to use curved rear mudguards, while Arkansas and other states required straight mudguards on the same routes. Navajo Freight Lines (plaintiff), an interstate trucking company, challenged the Illinois requirement enforced by Bibb (defendant), arguing that forcing trucks to swap mudguards at state lines was an excessive burden on interstate commerce. The district court agreed and struck down the law, and Illinois appealed.