The Consolidated Freightways Corporation of Delaware v. Kassel et al., 1981, was a U.S Supreme Court case that dealt with the issue of interstate commerce and state regulation. The dispute arose when Iowa enforced a law prohibiting the use of 65-foot double trailers on its highways, while neighboring states allowed them. This forced trucking companies to either unload and reload goods onto smaller trucks or detour around the state, both costly options. Consolidated Freightways sued arguing this violated their constitutional right to free trade among states (interstate commerce). The court ruled in favor of Consolidated Freightways by a narrow margin (5-4), finding that Iowa's law placed an undue burden on interstate commerce as it did not contribute significantly to highway safety - which was its intended purpose - but rather created unnecessary cost and inefficiency for transport businesses.

In the dissenting opinion for Consolidated Freightways Corporation of Delaware v. Kassel et al., Justice Rehnquist, joined by Chief Justice Burger and Justices Stewart and Powell, argued that the majority had overstepped its bounds in striking down an Iowa statute regulating truck size. The dissenters believed that this was a matter best left to state legislatures rather than federal courts. They pointed out that states have traditionally been allowed to regulate their own highways due to differing local conditions and needs. Furthermore, they disagreed with the majority's interpretation of previous case law as establishing a balancing test between state interests and burdens on interstate commerce; instead, they viewed these cases as upholding reasonable safety regulations even if they incidentally affected commerce. Finally, while acknowledging potential economic impacts on interstate trucking companies like Consolidated Freightways Corporation of Delaware from varying state regulations, the dissenters suggested such issues could be better addressed through national uniform standards enacted by Congress rather than judicial intervention.