Back in 2016, The Internet Archive published a national security letter it had received from the FBI that, among other things, included erroneous information about the process for challenging the letter.
According to a story published in The Intercept at the time,
So after the FBI sent the Internet Archive the NSL in August, demanding the name, address, length of service and a list of all accounts used by one of the archive’s supposed subscribers, the archive and the EFF sent the bureau a letter challenging the legality and constitutionality of the NSL and gag order. They also disclosed in the letter that the archive didn’t possess any records that matched the FBI’s request. Archive subscribers can use their accounts to upload contributions of books, music and other digital material or to comment on material others have uploaded. But the archive had no records of a subscriber matching the FBI’s target.
. . .
Kahle told The Intercept that the incident should encourage others to challenge NSLs and gag orders in the interest of transparency.
“We would like to see more of these come to light so we understand more of the workings of the government,” he said. “All we get [now] is a tiny peek. We’re appreciative of at least having this much light on the process, but what we’d like to see is a lot more.”