Ex parte Hung Hang was a United States Supreme Court case that dealt with the issue of whether a Chinese immigrant was entitled to naturalization. The case was brought by Hung Hang, a Chinese immigrant who had been living in the United States for over twenty years. He had applied for naturalization but was denied due to the Chinese Exclusion Act of 1882, which prohibited Chinese immigrants from becoming naturalized citizens. The Supreme Court held that the Chinese Exclusion Act was unconstitutional and that Hung Hang was entitled to naturalization. The Court reasoned that the Act violated the Equal Protection Clause of the Fourteenth Amendment, which prohibits the government from denying any person the equal protection of the laws. The Court also held that the Act was a form of racial discrimination and that it was not a legitimate exercise of the government's power to regulate immigration. The Court's decision in Ex parte Hung Hang was a landmark ruling that established the principle that the government cannot deny any person the equal protection of the laws. The ruling also helped to pave the way for the eventual repeal of the Chinese Exclusion Act in 1943.

In Ex Parte Hung Hang, the Supreme Court was asked to determine whether a Chinese man who had been convicted of violating California's anti-Chinese labor law could be denied entry into the United States. The majority opinion held that he could not be excluded because his conviction did not constitute an offense against morality or good order and thus did not fall within any exclusionary categories established by Congress. In dissent, Justice Field argued that it was well within Congress' power to exclude persons from entering the country based on their convictions for offenses which were deemed immoral or contrary to public policy. He further noted that while this particular case involved a Chinese national, similar laws existed in other states which prohibited certain classes of people from engaging in certain activities and those individuals should also be subject to exclusion if they violated such laws. Ultimately, Justice Field concluded that since Congress had given broad discretion over immigration matters to executive officers charged with enforcing immigration statutes, these officers should have authority when determining whether someone is eligible for admission into the United States.