https://arstechnica.com/tech-policy/2020/12/cbps-warrantless-use-of-cell-phone-location-data-is-under-investigation/

The Department of Homeland Security (DHS) inspector general is investigating the government's use of cell phone location data obtained without search warrants.

US Customs and Border Protection (CBP), a division of DHS, "has paid a government contractor named Venntel nearly half a million dollars for access to a commercial database containing location data mined from applications on millions of Americans' mobile phones," five Democratic US senators said in October.