## Facts

- In March 1880, Henry Youmans, John A. Connelly, and George Arnold (U.S. nationals) worked on the San Hilario Tunnel project in Angangueo, Michoacán, Mexico.
- A dispute over unpaid wages led Connelly to expel a Mexican laborer from his house; a violent confrontation followed in which Connelly fired shots and wounded the laborer while resisting entry.
- A large mob formed and surrounded the house where the three Americans took refuge.
- A representative of Connelly’s employer sought protection from local officials, including the mayor, but authorities did not effectively disperse or control the crowd.
- Mexican armed forces arrived; instead of protecting the Americans, they opened fire, and all three Americans were killed, by the forces and/or the mob.
- After the killings, no one was effectively punished, despite indications that some proceedings were initiated.
- The United States presented a claim on behalf of Thomas H. Youmans (son of Henry Youmans) seeking compensation from Mexico for the death and for failures of protection and post-incident enforcement.

## Issues

1. Whether Mexico incurs international responsibility when its armed forces, rather than protecting foreign nationals from a mob, participate in violence that results in their deaths.
2. Whether Mexico’s failure to exercise due diligence to prevent or control mob violence against foreign nationals constitutes an internationally wrongful omission.
3. Whether Mexico’s failure effectively to apprehend and punish those responsible constitutes a denial of justice engaging state responsibility.

## Decision

- The United States–Mexico General Claims Commission allowed the claim and held Mexico internationally responsible.
- The Commission treated the conduct of Mexican forces acting under an officer during a public-order disturbance as attributable to Mexico.
- The Commission concluded that Mexico failed to provide effective protection against the mob and that the subsequent lack of effective punishment supported responsibility.
- Compensation was awarded to the United States on behalf of Thomas H. Youmans (amount not specified in the materials summarized).

## Legal Principles

- A state bears responsibility for wrongful acts of its armed forces when they act in an official capacity or under command, including during internal disturbances.
- When foreign nationals face mob violence, the state must exercise due diligence to provide protection; ineffective or unwilling police action can constitute an internationally wrongful omission.
- Failure to investigate, prosecute, or punish serious violence against aliens may constitute a denial of justice and can independently support international responsibility.
- A combination of official participation in violence, inadequate protective measures, and post-incident impunity can establish state liability for injuries to foreign nationals.

## Conclusion

The Commission held Mexico liable for the killing of U.S. nationals where Mexican forces opened fire instead of providing protection and where authorities failed to secure accountability afterward, applying attribution to state organs, a due-diligence duty to protect against mob violence, and denial-of-justice principles based on ineffective punishment.


Thomas H. Youmans (U.S.) v. United Mexican States, 4 R.I.A.A. 110 (U.S.-Mex. Gen. Claims Comm’n 1926)