Mclaughlin v. United States was a case heard by the United States Supreme Court in 1883. The case involved a dispute between the United States and Mclaughlin, a citizen of the United States, over the ownership of a parcel of land in the state of California. Mclaughlin claimed that he had purchased the land from the Mexican government prior to the Mexican-American War, and thus had a valid title to the land. The United States argued that the land had been acquired by the United States as part of the Treaty of Guadalupe Hidalgo, which ended the war, and thus the United States had a valid title to the land. The Supreme Court held that the United States had a valid title to the land, as the Treaty of Guadalupe Hidalgo had been ratified by both the United States and Mexico, and thus the United States had acquired the land as part of the treaty. The Court also held that Mclaughlin's claim to the land was invalid, as he had not obtained a valid title from the Mexican government prior to the war. The Court thus ruled in favor of the United States.

Justice Field delivered the dissenting opinion in McLaughlin v. United States, arguing that Congress had no authority to pass a law criminalizing polygamy under the Constitution. He argued that while Congress could regulate marriage and divorce laws within territories, it did not have the power to make any act of bigamy or polygamy a crime because such acts were not prohibited by either state or federal constitutions. Furthermore, he argued that this was an issue for states to decide as they are better equipped than federal government when it comes to regulating morality-based issues like marriage and family life. Justice Field concluded his dissent by stating that if Congress wanted to prohibit polygamous marriages then it should amend the Constitution instead of passing legislation which is beyond its powers granted by the document itself.