Article VI, Clause 2:
This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.
The first significant extension of the doctrine of the immunity of federal instrumentalities from state taxation came in Weston v. Charleston, 1 where Chief Justice Marshall also found in the Supremacy Clause a bar to state taxation of obligations of the United States. During the Civil War, when Congress authorized the issuance of legal tender notes, it explicitly declared that such notes, as well as United States bonds and other securities, should be exempt from state taxation. 2 A modified version of this section remains on the statute books today. 3 The right of Congress to exempt legal tender notes to the same extent as bonds was sustained in Bank v. Supervisors, 4 over the objection that such notes circulate as money and should be taxable in the same way as coin. But a state tax on checks issued by the Treasurer of the United States for interest accrued upon government bonds was sustained since it did not in any way affect the credit of the National Government. 5 Similarly, the assessment for an ad valorem property tax of an open account for money due under a federal contract, 6 and the inclusion of the value of United States bonds owed by a decedent, in measuring an inheritance tax, 7 were held valid, since neither tax would substantially embarrass the power of the United States to secure credit. 8 A state property tax levied on mutual savings banks and federal savings and loan associations and measured by the amount of their capital, surplus, or reserve and undivided profits, but without deduction of the value of their United States securities, was voided as a tax on obligations of the Federal Government. Apart from the fact that the ownership interest of depositors in such institutions was different from that of corporate stockholders, the tax was imposed on the banks which were solely liable for payment thereof. 9
Income from federal securities is also beyond the reach of the state taxing power as the cases now stand. 10 Nor can such a tax be imposed indirectly upon the stockholders on such part of the corporate dividends as corresponds to the part of the corporation's income which is not assessed, i.e., income from tax exempt bonds. 11 A state may constitutionally levy an excise tax on corporations for the privilege of doing business, and measure the tax by the property of net income of the corporation, including tax exempt United States securities or the income derived therefrom. 12 The designation of a tax is not controlling. 13 Where a so-called
license tax upon insurance companies, measured by gross income, including interest on government bonds, was, in effect, a commutation tax levied in lieu of other taxation upon the personal property of the taxpayer, it was still held to amount to an unconstitutional tax on the bonds themselves. 14