Inc. South Carolina State Highway Department v. Barnwell Bros.

Writing for the Court, Justice Stone noted that "few subjects of state regulation are so peculiarly of local concern as is the issue of state highways . . . The state has a primary and immediate concern in their safe and economical administration." Despite that, South Carolina's restrictions may have been unconstitutional if they had contradicted congressional guidelines on the weight and width of trucks. However, the Motor Carrier Act, passed by Congress in 1935, did not set national standards for trucks, so the states were free to set their own. In addition, the state established those guidelines to ensure safety on the highways, and in this case that safety issue outweighed any burden on interstate commerce.

Another key point was whether the South Carolina regulations discriminated against interstate businesses, thereby giving state firms an unfair competitive advantage. All trucks, however, were subject to the restrictions. Stone commented, "The fact that [the regulations] affect alike shippers in interstate and intrastate commerce in large number within as well as without the state is a safeguard against their abuse."

Underlying that sentiment was the assumption that if the regulations were grossly unfair, South Carolina truckers could use their political influence in the state legislature to have the laws changed. The Court, however, should not be involved in determining if the details of the statute were reasonable, once it had established that the state did have the right to pass them. Stone wrote:

When the action of a Legislature is within the scope of its power, fairly debatable questions as to its reasonableness, wisdom, and propriety are not for the determination of courts, but for the legislative body . . . It is not any the less a legislative power committed to the states because it affects interstate commerce, and courts are not any more entitled, because interstate commerce is affected, to substitute their own for the legislative judgment.

After losing their case in the Supreme Court, the appellees and other South Carolina truckers did just as Stone implied: they went to the state legislature. Three months after the Supreme Court decision, the South Carolina legislature expanded its width and weight regulations for trucks.