What does the US Constitution say about birthright citizenship?

All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

That the said Wong Kim Ark was born in the year 1873, at No. 751 Sacramento Street, in the city and county of San Francisco, State of California, United States of America, and that his mother and father were persons of Chinese descent and subjects of the Emperor of China, and that said Wong Kim Ark was and is a laborer.

That, at the time of his said birth, his mother and father were domiciled residents of the United States, and had established and enjoyed a permanent domicil and residence therein at said city and county of San Francisco, State aforesaid.

That said mother and father of said Wong Kim Ark continued to reside and remain in the United States until the year 1890, when they departed for China.

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.

That ever since the birth of said Wong Kim Ark, at the time and place hereinbefore stated and stipulated, he has had but one residence, to-wit, a residence in said State of California, in the United States of America, and that he has never changed or lost said residence or gained or acquired another residence, and there resided claiming to be a citizen of the United States.

That, in the year 1890 the said Wong Kim Ark departed for China upon a temporary visit and with the intention of returning to the United States, and did return thereto on July 26, 1890, on the steamship Gaelic, and was permitted to enter the United States by the collector of customs upon the sole ground that he was a native-born citizen of the United States.

That after his said return, the said Wong Kim Ark remained in the United States, claiming to be a citizen thereof, until the year 1894, when he again departed for China upon a temporary visit, and with the intention of returning to the United States, and did return thereto in the month of August, 1895, and applied to the collector of customs to be permitted to land, and that such application was denied upon the sole ground that said Wong in Ark was not a citizen of the United States.

That said Wong Kim Ark has not, either by himself or his parents acting for him, ever renounced his allegiance to the United States, and that he has never done or committed any act or thing to exclude him therefrom.

...The real object of the Fourteenth Amendment of the Constitution, in qualifying the words, "All persons born in the United States" by the addition "and subject to the jurisdiction thereof," would appear to have been to exclude, by the fewest and fittest words (besides children of members of the Indian tribes, standing in a peculiar relation to the National Government, unknown to the common law), the two classes of cases -- children born of alien enemies in hostile occupation and children of diplomatic representatives of a foreign State -- both of which, as has already been shown, by the law of England and by our own law from the time of the first settlement of the English colonies in America, had been recognized exceptions to the fundamental rule of citizenship by birth within the country. ...

The words "in the United States, and subject to the jurisdiction thereof" in the first sentence of the Fourteenth Amendment of the Constitution must be presumed to have been understood and intended by the Congress which proposed the Amendment, and by the legislatures which adopted it, in the same sense in which the like words had been used by Chief Justice Marshall in the well known case of The Exchange and as the equivalent of the words "within the limits and under the jurisdiction of the United States," and the converse of the words "out of the limits and jurisdiction of the United States" as habitually used in the naturalization acts. This presumption is confirmed by the use of the word "jurisdiction" in the last clause of the same section of the Fourteenth Amendment, which forbids any State to "deny to any person within its jurisdiction the equal protection of the laws." It is impossible to construe the words "subject to the jurisdiction thereof" in the opening sentence, as less comprehensive than the words "within its jurisdiction" in the concluding sentence of the same section; or to hold that persons "within the jurisdiction" of one of the States of the Union are not "subject to the jurisdiction of the United States."...

In a very recent case, the Supreme Court of New Jersey held that a person born in this country of Scotch parents who were domiciled but had not been naturalized here was "subject to the jurisdiction of the United States" within the meaning of the Fourteenth Amendment, and was "not subject to any foreign power" within the meaning of the Civil Rights Act of 1866; and, in an opinion delivered by Justice Van Syckel with the concurrence of Chief Justice Beasley, said:

The object of the Fourteenth Amendment, as is well known, was to confer upon the colored race the right of citizenship. It, however, gave to the colored people no right superior to that granted to the white race. The ancestors of all the colored people then in the United States were of foreign birth, and could not have been naturalized or in any way have become entitled to the right of citizenship. The colored people were no more subject to the jurisdiction of the United States, by reason of their birth here, than were the white children born in this country of parents who were not citizens. The same rule must be applied to both races, and unless the general rule, that, when the parents are domiciled here, birth establishes the right to citizenship, is accepted, the Fourteenth Amendment has failed to accomplish its purpose, and the colored people are not citizens. The Fourteenth Amendment, by the language, "all persons born in the United States, and subject to the jurisdiction thereof," was intended to bring all races, without distinction of color, within the rule which prior to that time pertained to the white race. ...

The fact, therefore, that acts of Congress or treaties have not permitted Chinese persons born out of this country to become citizens by naturalization, cannot exclude Chinese persons born in this country from the operation of the broad and clear words of the Constitution, "All persons born in the United States, and subject to the jurisdiction thereof, are citizens of the United States."