Oath of Office
Clause 3. The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution; but no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States.
Power of Congress in Respect to Oaths
Congress may require no other oath of fidelity to the Constitution, but it may add to this oath such other oath of office as its wisdom may require.178 It may not, however, prescribe a test oath as a qualification for holding office, such an act being in effect an ex post facto law,179 and the same rule holds in the case of the states.180
178 McCulloch v. Maryland, 17 U.S. (4 Wheat.) 316, 416 (1819).
179 Ex parte Garland, 71 U.S. (4 Wall.) 333, 337 (1867).
180 Cummings v. Missouri, 71 U.S. (4 Wall.) 277, 323 (1867). See also Bond v. Floyd, 385 U.S. 116 (1966), in which the Supreme Court held that antiwar statements made by a newly elected member of the Georgia House of Representatives were not inconsistent with the oath of office to support to the United States Constitution.