In the 1906 U.S. Supreme Court case of Cahen v. Brewster, Tax Collector, a dispute arose over taxation on imported goods. The plaintiff, Cahen, was an importer who had paid duties under protest on certain imported merchandise to the defendant tax collector in San Francisco. He claimed that he was entitled to free entry for his goods under a treaty between France and the United States but was denied by customs officials who imposed duty charges based on domestic laws inconsistent with this treaty. Cahen sued for recovery of these duties arguing that they were illegally exacted from him as per Article VIII of Treaty of Commerce and Navigation (1860) between US and France which provided most-favored-nation treatment i.e., any privilege given by either country to another would be available to each other automatically. The Supreme Court held that while treaties are indeed part of supreme law land, Congress has power over commerce regulation including import tariffs & can modify or abrogate rights arising out such treaties through legislation without violating Constitution's Supremacy Clause; hence no refund is due if Congress enacted contrary statute after treaty came into effect. Therefore it ruled against Cahen stating that despite existing international agreements like aforementioned one with France , Congressional statutes supersede them when it comes to imposing taxes/duties domestically thereby affirming lower court decision denying refund claim made by plaintiff-importer.

In the dissenting opinion for Cahen v. Brewster, Tax Collector, 1906, it was argued that the majority's decision to uphold a tax on out-of-state corporations doing business in California violated constitutional principles of interstate commerce. The dissenting justices believed that this taxation constituted an unfair burden on businesses from other states and could potentially lead to retaliatory taxes by those states against Californian businesses. They also expressed concern about the potential for such taxes to disrupt national economic unity and create trade barriers between states. Furthermore, they disagreed with the majority's interpretation of what constitutes "doing business" within a state - arguing that merely having agents or representatives present does not necessarily equate to conducting operations there. Therefore, they felt that many companies were being unjustly taxed under this broad definition.