In the United States v. Barber case of 1890, the Supreme Court ruled on a matter concerning import duties and taxation. The defendant, Barber, was an importer who had been charged with paying import duties on goods that were not physically present in the U.S., but rather were stored in bonded warehouses at the time when tariffs were increased by new legislation. He argued against this charge claiming that he should not be required to pay additional taxes as his goods had arrived before the tariff increase took effect. The Supreme Court disagreed with Barber's argument and upheld his duty charges. They reasoned that while it is true that imported items are technically within U.S borders once they reach bonded warehouses, these items have not officially entered into circulation until all necessary customs procedures are completed - including payment of any applicable duties or taxes. Therefore, since Barber’s merchandise was still undergoing customs processing when new tariffs came into effect; it was subject to those higher rates despite having arrived prior to their enactment. This decision affirmed government authority over imports and clarified how changes in tax law apply to goods held under bond.

In the dissenting opinion for United States v. Barber, Justice Lamar disagreed with the majority's interpretation of Article IV, Section 2 of the Constitution and its application to state taxation laws. He argued that this section was intended to prevent states from discriminating against citizens of other states in terms of basic rights and privileges but did not intend to prohibit a state from imposing taxes on non-residents conducting business within its borders. According to him, such an interpretation would infringe upon a state's sovereignty by limiting its ability to regulate commerce within its boundaries as it saw fit. Furthermore, he contended that if Congress had intended for interstate commerce regulations under Article I, Section 8 to supersede individual state tax laws regarding non-resident businesses or professionals operating within their jurisdictions they would have explicitly stated so in the Constitution.