In the case of New York et al. v. United States et al., 1946, the Supreme Court ruled on a dispute over federal versus state authority in regulating interstate commerce. The issue at hand was whether or not states could impose taxes and regulations on milk dealers who bought milk from farmers outside of their respective states for sale within them, which would effectively control prices and potentially limit competition from out-of-state producers. The court held that such practices were unconstitutional as they interfered with Congress's exclusive power to regulate interstate commerce under the Commerce Clause of the Constitution (Article I, Section 8). This decision reinforced federal supremacy over state laws in matters related to interstate trade.

In the dissenting opinion for New York et al. v. United States et al., Justice Frankfurter argued that the majority's decision to strike down a federal tax on margarine was incorrect because it violated principles of federalism and states' rights. He believed that Congress had the power to impose such a tax under its constitutional authority to regulate interstate commerce, and he disagreed with the majority's interpretation of this power as being limited by state laws regulating local trade in dairy products. Furthermore, he contended that if every time there is an overlap between state and federal regulation, then only one can survive; this would lead to unnecessary conflicts between different levels of government which could undermine national unity and economic stability. Therefore, according to him, both should be able to coexist unless there is direct conflict or contradiction between them.