1806 is Correct.
"Articles of War...Article 25. No Officer or soldier shall send a challenge to another officer or soldier, to fight a duel, or accept a challenge, if sent, upon pain, if a commissioned officer, of being cashiered; if a non-commissioned officer or soldier, of suffering corporeal punishment, at the discretion of a court martial."
Article 26 and 28 also addresses Dueling.
The articles of War above were signed:
"Nathl. Macon, Speaker of the House of Representatives.
S.Smith President of the Senate, pro tempore.
April 10, 1806
Approved, Th: Jefferson"
The above is from my "Military Laws and Rules and Regulations for the armies of the United States. Adjutant and inspector General's office, Washington, May 1st, 1813"
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