United States ex rel. Angarica v. Bayard is a United States Supreme Court case that dealt with the issue of whether a person who had been convicted of a crime in a foreign country could be extradited to the United States to face criminal charges. The case involved a man named Angarica, who had been convicted of a crime in Mexico and was then extradited to the United States to face criminal charges. The Supreme Court held that the extradition was valid, and that the United States had the right to extradite a person who had been convicted of a crime in a foreign country. The Court reasoned that the extradition was valid because the United States had a treaty with Mexico that allowed for extradition of persons convicted of crimes in Mexico. The Court also noted that the extradition was in accordance with the principles of international law, which allow for extradition of persons convicted of crimes in foreign countries. The Court also noted that the extradition was in the interests of justice, as it would allow the United States to prosecute a person who had committed a crime in a foreign country. In conclusion, the Supreme Court held that the extradition of Angarica was valid, and that the United States had the right to extradite a person who had been convicted of a crime in a foreign country. The Court reasoned that the extradition was in accordance with the principles of international law, and that it was in the interests of justice.

In United States Ex Rel. Angarica v. Bayard, the Supreme Court was asked to determine whether a Spanish subject who had been naturalized as an American citizen could be extradited from the United States for alleged crimes committed in Spain prior to his naturalization. The majority opinion held that extradition of such persons is not prohibited by law and may be granted if requested by a foreign government under certain conditions. Justice Field dissented, arguing that while it is true that Congress has authorized extradition of citizens when they have violated laws abroad before their naturalization, this does not necessarily mean that all requests must be honored without exception or consideration of any other factors involved in the case at hand. He argued further that allowing extradition would violate due process rights since it would deprive individuals of their liberty without affording them adequate protection against arbitrary action on behalf of another country's government; he also noted potential conflicts between US and foreign laws which should be taken into account before granting any request for extradition involving a former alien now holding US citizenship status.