Actually, you have missed the mark a bit. They are in our jurisdiction physically, and thus are subject to enforcement of our laws. Besides, the Constitution states that a person is a US citizen under two conditions: sanguis or "by the blood" if you are born either on US soil or born to legal US citizens no matter where they are located at the time, and naturalized if you undergo the process of changing citizenship as written into law by the Congress, enforced by the President, and interprteted by the Courts. Currently the enforcement part is what is sadly lacking.