## Facts

- After the 1848 Treaty of Guadalupe Hidalgo, Mexican nationals residing in ceded territory could retain Mexican nationality by timely declaration; otherwise they were treated as having elected U.S. citizenship.
- Pablo de la Guerra was a Mexican citizen living in California at the time of the Treaty and did not declare an intent to retain Mexican citizenship.
- In 1869, de la Guerra was elected a California district judge.
- A California statute (Act of Apr. 20, 1863) required district judges to be “citizens of the United States.”
- The People, on relation of M. M. Kimberly, brought a proceeding in the nature of quo warranto to challenge de la Guerra’s right to hold office, arguing the Treaty did not itself make him a U.S. citizen absent further congressional action.
- The trial court found de la Guerra was a U.S. citizen and entitled to the office; the relator appealed.

## Issues

1. Whether Mexican residents of California covered by the Treaty of Guadalupe Hidalgo who did not elect to retain Mexican citizenship became U.S. citizens by operation of the Treaty, without an additional act of Congress.
2. Whether de la Guerra satisfied the statutory requirement that a California district judge be a “citizen of the United States.”

## Decision

- The California Supreme Court affirmed the judgment for de la Guerra.
- The court held that, for Mexican residents who remained in the ceded territory and did not declare an intent to retain Mexican citizenship, U.S. citizenship followed by force of the Treaty itself.
- The court concluded de la Guerra was a U.S. citizen and therefore eligible for the district judgeship under the 1863 statute.

## Legal Principles

- Treaty provisions governing nationality can be self-executing where their text and structure indicate immediate legal effect without further legislative implementation.
- Under the Treaty of Guadalupe Hidalgo, Mexican nationals residing in ceded territory who did not timely elect to remain Mexican nationals became U.S. citizens by operation of the Treaty.
- The Treaty’s nationality framework was construed to avoid any interval in which affected inhabitants would lack a national citizenship.
- A person who obtained U.S. citizenship through the Treaty satisfied state-law officeholding requirements conditioned on U.S. citizenship.

## Conclusion

The court upheld de la Guerra’s right to serve as district judge, ruling that the Treaty of Guadalupe Hidalgo itself conferred U.S. citizenship on qualifying Mexican residents of California who did not elect to retain Mexican nationality, and no separate act of Congress was required.


People ex rel. Kimberly v. De La Guerra, 40 Cal. 311 (Cal. 1870)