In the 1920 case of Philadelphia & Reading Railway Company v. Polk, the U.S Supreme Court was tasked with determining whether a Pennsylvania law that required railroads to compensate their employees for time spent traveling to and from work violated the Commerce Clause of the Constitution. The railway company argued that this state regulation interfered with interstate commerce by imposing additional costs on companies engaged in such activities. However, Justice Joseph McKenna delivered an opinion rejecting this argument and upholding the validity of Pennsylvania's law. He reasoned that while states cannot directly regulate interstate commerce, they can enact laws affecting it indirectly if those laws are primarily aimed at protecting public health or safety within their borders. In this instance, he found that ensuring workers were compensated for all time worked served a legitimate local purpose and did not unduly burden interstate commerce.

The dissenting opinion in the case of Philadelphia & Reading Railway Company v. Polk argued that the majority's decision was a departure from established legal principles and precedent. The dissent contended that it was not within the purview of federal courts to interfere with state laws regarding employer liability, unless those laws were clearly unconstitutional or violated rights protected by federal law. In this case, Pennsylvania’s Workmen’s Compensation Act had been upheld as constitutional by both state and federal courts previously. Therefore, according to the dissenting justices, there was no basis for overturning its application in this instance simply because it imposed on employers an absolute liability for injuries sustained by employees during work-related travel. They believed such matters should be left to legislative discretion rather than judicial interpretation.