Cavazos v. Trevino was a United States Supreme Court case that dealt with the issue of whether a Mexican citizen who had been living in the United States for many years was entitled to the same rights as a naturalized citizen. The case was brought by Jose Cavazos, a Mexican citizen who had been living in the United States since 1845. Cavazos had married a United States citizen and had children with her, but he had never been naturalized. He sued the United States government for the right to own land, claiming that he was entitled to the same rights as a naturalized citizen. The Supreme Court ruled in favor of Cavazos, finding that he was entitled to the same rights as a naturalized citizen. The Court held that the Fourteenth Amendment, which guarantees equal protection under the law, applied to all persons, regardless of their citizenship status. The Court also held that the United States government had a duty to protect the rights of all persons, regardless of their citizenship status. The ruling in Cavazos v. Trevino was an important step in the recognition of the rights of non-citizens in the United States. It established that non-citizens were entitled to the same rights as citizens, and that the government had a duty to protect those rights. This ruling has been cited in numerous cases since, and has been used to protect the rights of non-citizens in the United States.

In Cavazos v. Trevino, the Supreme Court was asked to decide whether a Mexican land grant could be enforced in Texas after it had become part of the United States. The majority opinion held that such grants were not enforceable because they violated U.S. law and policy on public lands, which prohibited private ownership of them without congressional approval or other authorization from the federal government. However, Justice Field dissented from this decision and argued that Congress had never expressly forbidden enforcement of these grants in Texas; thus, he believed they should still be recognized as valid property rights under state law until Congress acted otherwise. He further noted that if there was any doubt about their validity due to changing political circumstances since Mexico's cession of its territory to the United States, then those doubts should have been resolved in favor of upholding existing property rights rather than disregarding them entirely without consideration for how doing so would affect individuals who relied upon them for their livelihoods and security