Customs and Border Protection (CBP) has told Sen. Ron Wyden that it plans to stop using commercially sourced smartphone location data at the end of this month, Wyden’s office told 404 Media.

For years CBP, like many other U.S. law enforcement agencies, has bought access to location data harvested from smartphones, which one former location data company worker previously told me is useful for tracking “herds of people.” Another previously said it can be used to monitor specific targets too. Since the agencies paid a commercial vendor for the data, the agencies have generally not acquired a warrant or other court order to obtain the information; a move that critics say skirts the Fourth Amendment.

It is unclear why exactly CBP is stopping the use of such data. But lawmakers and campaigners who have pushed back against CBP and other agencies’ purchase of location data are welcoming the news, while demanding more protections against data use in the future.