Would you please give me more details about the Court decision on this matter? When did this happen?
Although it is the currently implemented (and imo, foolish) practice, it is up to Congress to dictate whether a child born of illegal aliens in the U.S. is granted citizenship or not.
In fact, American Indians who were born on reservations in the United States were not recognized as U.S. Citizens untill Congress passed a bill giving them citizenship. I think that was back around 1907.
The ball is in their court. There is nothing in the Constitution and there is no ruling by the Supreme Court preventing Congress from changing the status quo.
"Neither the Constitution nor any subsequent Supreme Court decision compels birthright citizenship to be conferred upon children of illegal aliens or of nonimmigrants born in the United States."
http://tancredo.house.gov/irc/welcome.htm