In United States v. Moreno, the Supreme Court ruled that a Mexican citizen who had resided in California since before it became part of the United States was not subject to military conscription under the Union Army's draft laws during the Civil War. The case arose when Francisco Moreno, a native-born Mexican citizen living in California at the time of its admission into statehood, refused to comply with an order from his local provost marshal requiring him to register for military service. He argued that he was not subject to such orders because he was neither a naturalized nor native-born U.S. citizen and thus could not be drafted into service against his will without violating international law principles protecting foreign nationals from being forced into involuntary servitude by another nation’s government or army forces. In ruling on this issue, Chief Justice Salmon P Chase held that although Congress had authority over all persons within U.S borders regardless of their citizenship status, it did not have power “to force citizens or subjects of other countries into its armies." Therefore, Moreno could not be compelled by federal authorities to serve in any capacity against his will as long as he remained loyal and peaceful towards both Mexico and America

In United States v. Moreno, 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 "inhabitant" of that state and thus eligible for jury service. The majority opinion held that he was not eligible because he did not meet the definition of inhabitant as set forth in federal law at the time. In his dissenting opinion, Justice Field argued that Congress never intended to exclude Mexicans from eligibility for jury service simply because they were born outside U.S. borders and had resided in California prior to its admission into the Union; rather, their right to serve on juries should have been determined by their residence within a particular district or county where they lived when summoned for duty as jurors. He further noted that this interpretation would be consistent with both congressional intent and public policy considerations such as promoting justice among all citizens regardless of national origin or race