## Facts

- In April 1861, after secession and the attack on Fort Sumter, President Lincoln proclaimed a naval blockade of ports controlled by Confederate forces.
- Union naval forces seized multiple merchant vessels and cargoes in May–July 1861 for attempting to enter or depart blockaded Confederate ports.
- The seized property included ships and cargoes owned by Northern residents, Southern residents, and foreign neutrals.
- Federal district courts, sitting in admiralty, condemned the vessels and cargoes as lawful prize for blockade-running.
- Claimants appealed, arguing the blockade and seizures were void because Congress had not formally declared war when many captures occurred.
- Congress later enacted statutes in July and August 1861 addressing insurrection and approving prior presidential measures connected to the rebellion.

## Issues

1. Whether a “state of war” can exist as a matter of fact without a formal congressional declaration, including in a civil conflict.
2. Whether the President, before a declaration of war, may institute a naval blockade of ports held by insurgent forces and subject violating vessels to capture as prize.
3. Whether residents of territory controlled by Confederate forces could be treated as “enemies,” and whether neutrals could be bound by blockade rules upon notice.

## Decision

- The Court affirmed the prize condemnations and upheld the blockade (5–4).
- The Court held that a de facto state of war existed based on the scale of hostilities, even absent a formal declaration.
- The Court held the President could respond to armed rebellion and employ recognized war measures, including blockade and prize captures.
- The Court treated the blockade proclamation as conclusive evidence that the Executive recognized and confronted an actual war requiring such measures.
- The Court stated neutrals were bound to respect a lawful blockade once they had knowledge or notice; vessels in blockaded ports were presumed to have notice when the blockade commenced.
- The Court also relied, in part, on Congress’s subsequent approval of presidential actions as validating the measures.

## Legal Principles

- A state of actual war may exist without a formal declaration; this applies to civil war as well as foreign war.
- When the United States is met with organized armed hostility, the President, as Commander in Chief, may meet the attack and employ war powers recognized by the law of nations, including blockade.
- In a public civil war of sufficient magnitude, the government may exercise belligerent rights *jure belli* against the opposing force and treat persons residing in territory controlled by that force as enemies for war purposes.
- A blockade is enforceable against neutral shipping when a state of war exists and the neutral has knowledge or notice of the blockade.
- Congressional ratification may validate prior executive measures taken in response to rebellion, though the majority treated presidential authority as already sufficient once actual war existed.

## Conclusion

The Court held that the Civil War created a de facto state of war triggering belligerent rights, allowing the President to impose and enforce a naval blockade and to condemn blockade-running vessels as prize even before Congress formally declared war.


The Prize Cases, 67 U.S. (2 Black) 635 (1863)