American intelligence agencies quietly stopped the warrantless collection of US phone location data last year, according to a letter from the Office of the Director of National Intelligence released today.

“Significant constitutional and statutory issues,”

Last year, in a landmark decision, the Supreme Court ruled against authorities looking to search through electronic location data without a warrant. Citing the ruling, Sen. Ron Wyden (D-OR), a privacy hawk in Congress, wrote a letter to then-Director of National Intelligence Dan Coats asking how agencies like the National Security Agency would apply the court’s decision.

In a response to Wyden released today, a representative for the office said intelligence agencies have already stopped the practice of collecting US location data without a warrant. Previously, agencies collected that information through surveillance powers granted under the Patriot Act. But since the Supreme Court’s decision, the agencies have stopped the practice, and they now back up those searches through a warrant, under the legal standard of probable cause.

In the letter to Wyden, the intelligence community official writes that the Supreme Court’s decision presented “significant constitutional and statutory issues,” but would not explicitly rule out using the tools in the future. The letter says that “neither the Department of Justice nor the Intelligence Community has reached a legal conclusion” on the matter.

Next month, provisions of the Patriot Act — specifically, Section 215 — are set to expire, raising questions about potential reforms. “Now that Congress is considering reauthorizing Section 215, it needs to write a prohibition on warrantless geolocation collection into black-letter law,” Wyden said in a statement. “As the past year has shown, Americans don’t need to choose between liberty and security — Congress should reform Section 215 to ensure we have both.”