http://en.wikipedia.org/wiki/United_States_v._Wong_Kim_Ark

Quoted, notations omitted

United States v Wong Kim Ark (1898)

Facts
Wong Kim Arkwas born in San Francisco, California sometime between 1868 and 1873. His father, Wong Si Ping and his mother, Wee Lee were immigrants from Taishan, China and were not United States citizens.
In 1890 Wong’s parents returned to live in China. Later that year Wong himself traveled to China and, when he returned to the U.S., authorities granted him entry “upon the sole ground that he was a native-born citizen of the United States.” Four years later, however, the circumstances had changed, as Wong, who was employed in San Francisco as a cook, sailed to China on another temporary visit in 1894. When he returned to the U.S. in August 1895, he was detained at the Port of San Francisco by the Collector of Customs, who denied him permission to enter the country ? arguing that Wong, “although born in the city and county of San Francisco, state of California, United States of America, is not, under the laws of the state of California and of the United States, a citizen thereof, the mother and father of the said Wong Kim Ark being Chinese persons, and subjects of the emperor of China, and the said Wong Kim Ark being also a Chinese person and a subject of the Emperor of China.”

Opinion
In a 6-2 decision, the Court held that under the Fourteenth Amendment, a child born in the United States of parents of foreign descent who, at the time of the child’s birth are subjects of a foreign power but who have a permanent domicile and residence in the United States and are carrying on business in the United States, and are not employed in any diplomatic or official capacity under a foreign power, and are not members of foreign forces in hostile occupation of United States territory, becomes a citizen of the United States at the time of birth.

Rationale
The 14th Amendment’s citizenship clause, according to the court’s majority, had to be interpreted in light of English common law tradition that had excluded from citizenship at birth only two classes of people: (1 children born to foreign diplomats and ( 2 children born to enemy forces engaged in hostile occupation of the country’s territory. The majority held that the “subject to the jurisdiction” phrase in the 14th Amendment specifically encompassed these conditions (plus a third condition, namely, that Indian tribes were not considered subject to U.S. jurisdiction) – and that since none of these conditions applied to Wong’s situation, Wong was a U.S. citizen, regardless of the fact that his parents were not U.S. citizens (and were, in fact, ineligible ever to become U.S. citizens because of the Chinese Exclusion Act). The opinion emphasized the fact that “…during all the time of their said residence in the United States, as domiciled residents therein, the said mother and father of said Wong Kim Ark were engaged in the prosecution of business, and were never engaged in any diplomatic or official capacity under the emperor of China”.
Since Wong was a U.S. citizen from birth, the restrictions of the Chinese Exclusion Act did not apply to him. An act of Congress, the majority held, does not trump the Constitution; such a law “cannot control [the Constitution's] meaning, or impair its effect, but must be construed and executed in subordination to its provisions.”
Chief Justice Melville Fuller, in a dissenting opinion joined by Justice John Harlan, argued that the history of U.S. citizenship law had broken with English common law tradition after independence?citing as an example the embracing in the U.S. of the right of expatriation (giving up of one’s native citizenship) and the rejection of the contrary British doctrine of perpetual allegiance. The minority argued that the principle of Jus sanguinis (that is, the concept of a child inheriting his or her father’s citizenship by descent regardless of birthplace) had been more pervasive in U.S. legal history since independence.
Pointing to the language of the Civil Rights Act of 1866, which declared to be citizens “all persons born in the United States and not subject to any foreign power, excluding Indians not taxed”, and which was enacted into law only two months before the 14th Amendment was proposed by Congress, the minority argued that “it is not open to reasonable doubt that the words ‘subject to the jurisdiction thereof,’ in the amendment, were used as synonymous with the words ‘and not subject to any foreign power’ . . . .” They thus reasoned that the majority opinion exactly contradicted the original intended meaning of the 14th Amendment.
In the view of the minority, excessive reliance on Jus soli (birthplace) as the principal determiner of citizenship would lead to an untenable state of affairs in which “…the children of foreigners, happening to be born to them while passing through the country, whether of royal parentage or not, or whether of the Mongolian, Malay or other race, were eligible to the presidency, while children of our citizens, born abroad, were not”.
The dissenters acknowledged that other children of foreigners ? including freed slaves ? had, through the years, acquired U.S. citizenship through birth on U.S. soil. But they still saw a difference between those people and U.S.-born individuals of Chinese ancestry, because of strong cultural traditions discouraging Chinese immigrants from assimilating into mainstream American society, Chinese laws of the time which made acquiring a new citizenship or renouncing allegiance to the Chinese emperor a capital crime and the provisions of the Chinese Exclusion Act making Chinese immigrants already in the United States ineligible for citizenship.

It is directly responsible for the “anchor baby” thing. The case sited above is the first of a few that ripped apart the original meaning of “subject to the juristiction thereof”. Plyler v. Doe (1982) struck down a Texas law that attempted to deny children of illiegal immigrants public resources such as education.

Regardless of where one stands on the issues, I think we can all agree that the constitution means what it says, and we shouldn’t need to keep putting amendmens in that say it means what it says. The 14th amendment is somewhat of that, as an echo of Article 4 Section 2 which says: “The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States” with the exception that it defined what citizenship means and was written to overrule Dred Scott.