Wong Kim Ark, who was born in San Francisco to Chinese parents around 1871, had been denied re-entry to the United States after a trip abroad, under a law restricting Chinese immigration and prohibiting immigrants from China from becoming naturalized U.S. citizens. He challenged the government's refusal to recognize his citizenship, and the Supreme Court ruled in his favor, holding that the citizenship language in the Fourteenth Amendment encompassed essentially everyone born in the U.S.—even the U.S.-born children of foreigners—and could not be limited in its effect by an act of Congress.
The case highlighted disagreements over the precise meaning of one phrase in the Citizenship Clause—namely, the provision that a person born in the United States who is subject to the jurisdiction thereof acquires automatic citizenship. The Supreme Court's majority concluded that this phrase referred to being required to obey U.S. law; on this basis, they interpreted the language of the Fourteenth Amendment in a way that granted U.S. citizenship to almost all children born on American soil (a concept known as jus soli). The court's dissenters argued that being subject to the jurisdiction of the United States meant not being subject to any foreign power—that is, not being claimed as a citizen by another country via jus sanguinis (inheriting citizenship from a parent)—an interpretation which, in the minority's view, would have excluded "the children of foreigners, happening to be born to them while passing through the country".
In the words of a 2007 legal analysis of events following the Wong Kim Ark decision, "The parameters of the jus soli principle, as stated by the court in Wong Kim Ark, have never been seriously questioned by the Supreme Court, and have been accepted as dogma by lower courts." A 2010 review of the history of the Citizenship Clause notes that the Wong Kim Ark decision held that the guarantee of birthright citizenship "applies to children of foreigners present on American soil" and states that the Supreme Court "has not re-examined this issue since the concept of 'illegal alien' entered the language". Since the 1990s, however, controversy has arisen over the longstanding practice of granting automatic citizenship to U.S.-born children of illegal immigrants, and legal scholars disagree over whether the Wong Kim Ark precedent applies when alien parents are in the country illegally. Attempts have been made from time to time in Congress to restrict birthright citizenship, either via statutory redefinition of the term jurisdiction, or by overriding both the Wong Kim Ark ruling and the Citizenship Clause itself through an amendment to the Constitution, but no such proposal has been enacted.
