Four score and six years after the founding of the nation, during the Civil War, Congress passed a statute. The statute mandated that certain officeholders take a loyalty oath—this was a second oath, in addition to the ordinary oath prescribed by Congress pursuant to Article VI. The statute extended to “every person” holding “any office of honor or profit under the government of the United States.” The oath was passed during the Thirty-Seventh Congress. That Congress terminated on March 3, 1863. During that Congress, Senator James Asheton Bayard, Jr. (Delaware-Democrat) failed (or, perhaps, refused) to take the newly prescribed loyalty oath. Bayard was reelected in 1863.
When the first regular session of the new Congress met, Senator Sumner (Massachusetts-Republican) put forward a resolution requiring all senators to take the newly prescribed loyalty oath. Bayard refused to do so on a point of principle. Bayard contested the constitutionality of the statute (at least, as applied to members of Congress) and also its construction: i.e., Did the statute’s language reach members of Congress? Bayard made a variety of arguments. Bayard opened a copy of American State Papers, which was by then some three decades old, and on January 19, 1864, on the floor of the Senate, he proceeded to state . . . .
The paper can be found here: Seth Barrett Tillman, The Foreign Emoluments Clause, the Teachings of the American Civil War, and a Response to Mike Stern: The Aftermath of the Hamilton Documents Imbroglio (Feb. 21, 2018), https://ssrn.com/abstract=3126689.
Seth Barrett Tillman, The Foreign Emoluments Clause, the Teachings of the American Civil War, and a Response to Mike Stern: The Aftermath of the Hamilton Documents Imbroglio, New Reform Club (Feb. 21, 2018), http://reformclub.blogspot.ie/2018/02/the-foreign-emoluments-clause-teachings.html