Alviso v. United States was a case heard by the United States Supreme Court in 1866. The case involved a dispute between the United States and the Alviso family over the ownership of a piece of land in California. The Alviso family had been granted the land by the Mexican government in 1844, but the United States had claimed the land as part of the Treaty of Guadalupe Hidalgo in 1848. The Supreme Court ultimately ruled in favor of the United States, finding that the Treaty of Guadalupe Hidalgo had superseded the Mexican grant and that the United States had a valid claim to the land. The Court also held that the Alviso family had no right to the land, as they had not taken any steps to perfect their title to the land prior to the Treaty of Guadalupe Hidalgo. This case established the principle that the United States could acquire land from foreign governments through treaties, and that any prior grants of land by foreign governments would be superseded by such treaties.

In Alviso v. United States, the Supreme Court was asked to decide whether a Mexican citizen who had been living in California since before it became part of the United States could be considered an American citizen. The majority opinion held that he could not, as he did not meet any of the criteria for naturalization established by Congress at that time. However, Justice Field dissented from this decision and argued that under international law and treaties between Mexico and the U.S., citizens of one country were entitled to certain rights when they moved to another country's territory - including protection against being deprived of their property without due process or just compensation. He further argued that although Congress had authority over immigration matters, it did not have absolute power over citizenship status; rather, individuals should be able to prove their allegiance through other means such as long-term residence in a particular place or service in its military forces during wartime. As Alviso met both these requirements (he had lived continuously in California since 1846), Field concluded he should be granted citizenship rights regardless of his lack of formal naturalization papers