From EPIC.org:
FCC Chairman Pai has announced upcoming enforcement actions against wireless carriers that disclosed subscribers’ location data. Last year Members of Congress called an emergency briefing with the FCC and urged the agency to investigate companies that were selling subscribers’ location data. EPIC has long advocated for protection of location data. EPIC pursued a lawsuit against a mobile app company that led to greater protection of users’ location data. EPIC also successfully petitioned the FCC to safeguard sensitive data collected by phone companies. And EPIC filed a amicus brief in Carpenter v. US. The Supreme Court held in that case that the Fourth Amendment protects cell site location information. EPIC maintains detailed webpages on location privacy.