Journalists and free press advocates are responding with alarm to newly released documents revealing the U.S. government’s secret rules for using Foreign Intelligence Surveillance Act (FISA) court orders to spy on reporters, calling the revelations “important” and “terrifying.”

The documents—obtained and released by the Freedom of the Press Foundation and the Knight First Amendment Institute at Columbia University through an ongoing Freedom of Information Act (FOIA) lawsuit filed last November—confirm long held suspicions that federal officials can target journalists with FISA orders.

The two 2015 memos from former Attorney General Eric Holder to the Federal Bureau of Investigation (FBI) lay out procedures to ensure that the attorney general or deputy attorney general signs off on any FISA applications “targeting known media entities or known members of the media.”

These secret rules, as Cora Currier reported for The Intercept, “apply to media entities or journalists who are thought to be agents of a foreign government, or, in some cases, are of interest under the broader standard that they possess foreign intelligence information.”

“There’s a lack of clarity on the circumstances when the government might consider a journalist an agent of a foreign power,” Ramya Krishnan, a staff attorney with the Knight Institute told Currier. “Think about WikiLeaks; the government has said they are an intelligence operation.”

Additionally, even if they aren’t personally targeted by FISA orders, Krishnan pointed out that “journalists merely by being contacted by a FISA target might be subject to monitoring—these guidelines, as far as we can tell, don’t contemplate that situation or add any additional protections.”