Yahoo has just published three national security letters, controversial government demands for information usually accompanied by a gag order and rarely made public.

Disclosed two letters from 2013, and one from 2015

The company writes in a statement that it was able to publish the letters after changes made by the USA Freedom Act required the FBI to review nondisclosure requirements. Generally, tech companies have only been able to mention national security demands in "bands" of nonspecific numbers glimpsed in transparency reports. Last month, the FBI cleared Yahoo to acknowledge the three letters it made available today, although the personal information related to the accounts remains redacted.

Two of the disclosed letters were sent in 2013, and one was sent in 2015. All three were requests from the FBI for information related to Yahoo accounts. The company writes that it complied with all of the requests, providing information on the relevant name, address, and length of service tied to each account. (In the 2015 case, it did not find the relevant account in its system, and thus did not have any information to turn over.) The users, Yahoo writes, have been notified of the NSLs.

"Going forward, we will update our Transparency Report to include the number of NSLs received and number of accounts specified in those letters as the FBI lifts additional nondisclosure provisions," the company wrote in its statement.

Critics of NSLs have argued that the letters are a strikingly broad tool operating with little transparency or oversight. In one closely watched case, the owner of a small internet service provider fought a NSL gag order for more than a decade, and was only able to legally discuss it last year.