Congress voted June 2 to ban the NSA from collecting telephone records in bulk, ending a practice adopted following the Sept. 11, 2001, terror attacks. The law that ended the program, the USA Freedom Act, gave the NSA 180 days to transition into a new system, and that period expires Sunday.

Starting Monday, telephone companies will retain the call records and the government will have to seek individual information from them on a case-by-case basis, including obtaining a court order, when conducting an investigation.

The Office of the Director of National Intelligence, James R. Clapper, said Friday that the new system “allows national security professionals to retain the capabilities necessary to continue protecting the country, while strengthening the civil liberties protections that the American people cherish.”