In the case of McLean Trucking Co. et al. v. United States et al., 1943, the Supreme Court examined whether an order issued by the Interstate Commerce Commission (ICC) was in violation of antitrust laws and if it exceeded its authority under the Motor Carrier Act of 1935. The ICC had allowed a group of trucking companies to establish a collective rate-making body known as Middle Atlantic Conference (MAC). Several other trucking firms challenged this decision, arguing that it violated both Sherman Antitrust Act and Clayton Antitrust Act because MAC's activities could potentially lead to price-fixing or monopolistic practices within their industry. The Supreme Court upheld ICC’s decision stating that Congress intended for some cooperative rate-making among motor carriers when they passed Motor Carrier Act; therefore, such arrangements were not inherently illegal under antitrust laws provided they are regulated by ICC to prevent any anti-competitive behavior. The court also held that while individual members must retain freedom to act independently outside these agreements, there is no requirement for them to compete against each other on rates where cooperation has been approved.

The dissenting opinion in the case of McLean Trucking Co. et al. v. United States et al., 1943, argued that the Interstate Commerce Commission (ICC) had overstepped its authority by imposing restrictions on trucking companies' operations without sufficient evidence to justify such measures. The dissenters believed that the ICC's decision was arbitrary and lacked substantial support from factual findings or legal principles, thereby violating due process rights of the trucking companies involved in this case. They also expressed concerns about potential negative impacts on competition within the industry as a result of these regulations, arguing that they could lead to monopolistic practices and stifle innovation among smaller carriers who might not be able to comply with stringent requirements imposed by ICC orders.