[Ed. – Most of us would agree that our immigration laws need enforcement, and there’s nothing wrong in the narrow sense with using this method. It’s legitimate, however, to be concerned that growing accustomed to this level of surveillance carries serious dangers with it. Using electronic monitoring more and more freely against terrorists and drug cartels is exactly what got us to the back-door exploitation of national security methods in 2016 to intrusively monitor members of the Trump campaign for no good reason. This is an ugly problem because it starts out with no obvious solutions. But Congress needs to take it up soon (ideally in the next session if Republicans retake the House).]
The Trump administration has bought access to a commercial database that maps the movements of millions of cellphones in America and is using it for immigration and border enforcement, according to people familiar with the matter and documents reviewed by The Wall Street Journal.
The location data is drawn from ordinary cellphone apps, including those for games, weather and e-commerce, for which the user has granted permission to log the phone’s location.
The Department of Homeland Security has used the information to detect undocumented immigrants and others who may be entering the U.S. unlawfully, according to these people and documents.