In 2001, with the passage of the USA PATRIOT Act, Congress expanded the federal government’s ability to issue National Security Letters (“NSLs”) to companies that have information relevant to counter-intelligence or terrorism investigations.  NSLs often include a nondisclosure provision preventing the recipient from disclosing the NSL’s contents or the number of such NSLs received.  Recently, several technology companies have turned to the use of “warrant canaries”— statements or notices disclosing that no government requests have been received—to disclose limited information about NSLs that would otherwise be prohibited.

For several years, technology companies have challenged the government’s use of NSLs, citing concerns about improper requests, improper authorization, misstatements of fact and a general desire to notify customers to encourage public debate.  Currently, the Justice Department allows recipients to disclose only the number of NSLs received in a six-month window, and only in “bands of 1000 starting with 0-999” (e.g., a recipient of 408 NSLs may only disclose that it received 0-999 NSLs in the last six months).

Companies concerned about the utility of such broad ranges have turned to what are colloquially known as “warrant canaries.”  In theory, the nondisclosure requirements in an NSL attach only upon service, and a company that is not subject to such nondisclosure is free to report that it has not received any NSLs.  Once the “all clear” message disappears (the “canary in the coal mine” has stopped singing), the public will know that the company has received some number of NSLs.

Reportedly, the government has attempted to limit the use of warrant canaries, but some commentators have suggested that in general, warrant canaries should be legal.  At least one company has implemented a system whereby third parties must authenticate the warrant canary, so any government requirement to update or remove the warrant canary would need the cooperation of those third parties as well.  The exact circumstances in which warrant canaries legally may be employed has yet to be resolved by the courts.