Hepburn v. Griswold was a United States Supreme Court case that dealt with the issue of whether a state could tax the notes of a national bank. The case was brought by the Bank of the United States against the state of Connecticut, represented by the state's attorney general, William Griswold. The bank argued that the state's tax on its notes was unconstitutional, as it violated the Bank's right to be free from state taxation. The Supreme Court ruled in favor of the Bank, finding that the state's tax was unconstitutional. The Court held that the Bank was a federal instrumentality, and as such, was immune from state taxation. The Court reasoned that the Bank was created by Congress to serve a public purpose, and that the state's tax interfered with the Bank's ability to fulfill its purpose. The Court also held that the Bank's notes were not taxable under the Constitution, as they were issued by a federal instrumentality. The decision in Hepburn v. Griswold established the principle that states cannot tax the notes of a national bank. This principle has been applied in numerous cases since, and has been used to protect the Bank's ability to serve its public purpose.

In Hepburn v. Griswold, the Supreme Court was tasked with determining whether a federal tax on notes issued by state banks was constitutional. The majority opinion held that Congress had the power to impose such taxes under its authority to "lay and collect Taxes, Duties, Imposts and Excises." In his dissenting opinion, Justice Field argued that this interpretation of congressional taxation powers would lead to an unconstitutional expansion of federal power over states' rights. He argued that while Congress has broad authority in taxing matters related to foreign commerce or interstate trade, it does not have the same level of control when it comes to internal affairs within each state's borders. Furthermore, he noted that if allowed unchecked in this case then Congress could use similar reasoning for any other type of taxation they wished - regardless of how intrusive or oppressive it may be - thus leading to an erosion of states' rights as guaranteed by the Constitution.