Pierce Butler, Missouri Pacific Company v. Norwood…
“ Has Congress prescribed, or authorized the Interstate Commerce Commission to regulate, the number of brakemen to be employed for the operation of freight trains or the number of helpers to be included in switching crews?In the absence of a clearly expressed purpose so to do Congress will not be held to have intended to prevent the exertion of the police power of the states for the regulation of the number of men to be employed in such crews. ”
