In the case of Charles Nelson Company v. United States, 1922, the Supreme Court ruled on a dispute involving customs duties. The Charles Nelson Company imported iron and steel products from abroad and was charged with additional import duties by U.S. Customs under the Emergency Tariff Act of 1921. The company argued that these charges were incorrect as they had entered into contracts for these goods before this act came into effect; thus, their imports should be exempted from any additional tariffs imposed by it. The court held in favor of the United States government stating that regardless of when a contract was made or even if payment had been completed prior to shipment, what mattered was when those goods arrived at an American port because that's when duty is determined and collected according to existing laws at that time. This ruling established an important precedent in international trade law: contractual agreements do not supersede changes in tariff legislation - importers are subject to pay whatever rates are effective upon arrival of their merchandise.

In the dissenting opinion for Charles Nelson Company v. United States, Justice McReynolds disagreed with the majority's interpretation of Section 10 of the Lever Act. He argued that this section was not intended to apply to contracts made before its enactment and should only be applied prospectively, not retrospectively. According to him, interpreting it otherwise would lead to an unjust result where a party could escape their contractual obligations simply because they became more burdensome due to unforeseen circumstances such as war or inflation. This would undermine fundamental principles of contract law which hold parties accountable for their agreements regardless of subsequent events unless there is a specific provision in the contract allowing them an out under certain conditions.