Cheong Ah Moy v. United States was a Supreme Court case that addressed the issue of whether a Chinese immigrant was eligible for naturalization. The case was brought before the Supreme Court in 1885. At the center of the case was Cheong Ah Moy, a Chinese immigrant who had been living in the United States for over twenty years. He had applied for naturalization, but his application was denied by the Circuit Court of the United States for the Northern District of California. The court denied his application on the grounds that he was not a "free white person" as required by the naturalization laws of the time. The Supreme Court ultimately ruled in favor of Ah Moy, finding that the naturalization laws of the time did not explicitly exclude Chinese immigrants from naturalization. The Court held that the naturalization laws should be interpreted in a manner that was consistent with the spirit of the Constitution, which was to provide equal protection to all persons regardless of race or national origin. The Court's decision in Cheong Ah Moy v. United States was a landmark ruling that helped to expand the rights of Chinese immigrants in the United States. The ruling established that Chinese immigrants were eligible for naturalization and that the naturalization laws should be interpreted in a manner that was consistent with the spirit of the Constitution.

Justice Field delivered the dissenting opinion in Cheong Ah Moy v. United States, arguing that the majority's decision was contrary to both precedent and common sense. He argued that Congress had no authority to pass a law which would allow for naturalization of Chinese persons who were not citizens of any foreign country, as they did not meet the requirements set out by Congress in their original legislation. Furthermore, he noted that even if such an act could be passed by Congress it should have been done explicitly rather than impliedly through judicial interpretation of existing laws. Justice Field concluded his dissent with a warning against allowing courts to interpret statutes beyond what is written or intended by its authors and instead urged them to adhere strictly to statutory language when making decisions on matters like this one.