This view of the Constitution has been rejected by the federal courts, which consistently have held that under the Constitution, the states do not have the power to nullify federal laws. The courts have rejected the compact theory, finding that the Constitution was not a contract among the states.
A U.S. Border Patrol agent in San Diego has been arrested for hiding his undocumented father and other people in the U.S. illegally.
However, demographers have come up with ways to estimate the size of the illegal alien population. The Department of Homeland Security estimated that 11.4 million illegal aliens were living in the United States in 2012 (DHS, March 2013). Pew Research Center estimated that the illegal alien population in 2014 was 11.3 million (Pew, July 2015). Read more about Illegal Alien Population in the U.S. (2015) A definitive count of the number of illegal aliens living in the United States is difficult to obtain. For obvious reasons, those who are in the country illegally are reluctant to come forward to be identified and counted.