Dean v. Nelson was a United States Supreme Court case that was decided in 1870. The case involved a dispute between two parties over the ownership of a piece of land in the state of Missouri. The plaintiff, Dean, claimed that he had purchased the land from the defendant, Nelson, in 1867. Nelson, however, argued that he had never sold the land to Dean and that he was still the rightful owner. The Supreme Court ultimately sided with Dean, ruling that he had indeed purchased the land from Nelson in 1867. The Court found that Dean had provided sufficient evidence to prove that he had purchased the land from Nelson, including a deed of sale and a receipt for the purchase price. The Court also noted that Nelson had failed to provide any evidence to support his claim that he had not sold the land to Dean. As a result, the Court held that Dean was the rightful owner of the land.

In the case of Dean v. Nelson, the Supreme Court was asked to decide whether a state court had jurisdiction over a suit brought by an alien against another alien in which both parties were domiciled in the same foreign country. The majority opinion held that it did not have such jurisdiction and dismissed the appeal. In his dissenting opinion, Justice Field argued that since Congress had granted aliens living within its borders certain rights under international law, those same rights should be extended to aliens who are domiciled abroad but bring their cases before American courts. He further argued that if states could deny these individuals access to justice then they would effectively be violating federal laws protecting them from discrimination on account of their nationality or residence status. Ultimately, he concluded that denying this right would create two classes of citizens: one with full protection and one without any legal recourse whatsoever when wronged by another party residing outside of America's borders.