Government agencies are tracking smartphone users via the location gleaned from weather and other apps, reports the Wall Street Journal . The paper says the Trump administration has bought access to a commercial database that gives users the ability to access the location of millions of people. The WSJ says the database is currently being used by the Department of Homeland Security:

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.

One division of Homeland Security, the U.S. Customs and Border Protection, is reportedly using the location data games and apps report to marketing firms to look for smartphone use out of the ordinary places, like deserts between the U.S. and Mexican border in an attempt to catch illegal border crossings.

In 2018, the U.S. Supreme Court put limits on law enforcement agencies’ ability to collect location data from mobile network operators without a court overseeing the process. However, the WSJ says the federal government has found a way around that ruling–simply by purchasing location data from commercial marketing firms. Doing so allows them to sweep up massive amounts of location data without court supervision.

The Department of Homeland Security admitted to the WSJ that it has bought access to the database of location data provided by Venntel Inc., a firm that trades in mobile location data, but would not comment on how the database information is used.

The workaround is something that worries privacy experts, as Alan Butler, general counsel of the Electronic Privacy Information Center, told the WSJ: “This is a classic situation where creeping commercial surveillance in the private sector is now bleeding directly over into government.”