## Facts

- After President Abraham Lincoln’s assassination, President Andrew Johnson requested the Attorney General’s advice on whether alleged conspirators could be tried by a military tribunal or had to be tried in a civil court.
- Attorney General James Speed issued a formal written opinion in July 1865 addressing the constitutional basis for military commissions in these circumstances.
- The opinion treated the alleged assassins and co-conspirators as participants in a war-related conspiracy connected to the Confederate rebellion.
- Speed described wartime conditions in Washington, D.C., including active hostilities, extensive fortifications, and heavy military control over security and policing.
- Relying on the opinion, President Johnson convened a military commission of nine officers to try the accused conspirators in Washington, D.C.
- The military commission proceeded with trials; several defendants were sentenced to death and executed.

## Issues

1. Whether, during an ongoing civil war, alleged participants in the Lincoln assassination conspiracy could constitutionally be tried by military commission rather than in an Article III civilian court.
2. Whether the law of war is part of domestic law such that it can supply jurisdiction and substantive standards for military commissions.
3. Whether the accused could be classified as “public enemies” whose conduct constituted an offense against the laws of war rather than a civilian crime.
4. Whether the availability and operation of civilian courts in Washington, D.C., barred the use of a military commission.

## Decision

- Speed concluded the accused conspirators could be tried by a military commission.
- He reasoned that the law of war forms part of the law of the United States and is recognized within the constitutional structure governing wartime powers.
- He treated the conspiracy as an act of war by public enemies or enemy agents, bringing it within military jurisdiction.
- He advised that open civil courts did not necessarily eliminate military-commission jurisdiction when the charge concerned offenses against the laws of war committed by enemy belligerents or their agents.
- The opinion supported the President’s order establishing a military commission to conduct the trials.

## Legal Principles

- The law of war, as a component of the law of nations, may operate as domestic law in wartime and can authorize military adjudication of offenses against it.
- Military commissions may exercise jurisdiction over persons treated as enemy belligerents or public enemies for war-related offenses, including conspiracies directed at the government’s wartime leadership.
- The Commander-in-Chief’s wartime authority may include the use of military tribunals as an incident of conducting war and suppressing enemy action.
- The existence of functioning civilian courts does not, on this view, categorically preclude military jurisdiction when the case is framed as a law-of-war offense committed by enemy agents in a war environment.

## Conclusion

The Attorney General advised that, given ongoing war conditions and the characterization of the accused as public enemies acting under the law of war, the Constitution permitted trying the Lincoln assassination conspirators before a military commission, and the President relied on that advice to convene such a tribunal and proceed with military trials and punishments.


Constitutional Power of the Military to Try and Execute the Assassins of the President, 11 Op. Att’y Gen. 297 (1865)