The plain letter of it states:

  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.

The argument is that certain overseas territories, foreign dignitaries, and illegal immigrants are "not subject to the jurisdiction thereof." The first two are not offered birthright citizenship, the latter is. If consistency is to be considered, illegal aliens should similarly not be offered birthright citizenship.