Would it be illegal to withdraw a disclaimer that no "National Security Letters" requests have been made *today*?

Question

According to EFF:

By using NSLs, the FBI can directly order companies to turn over information about their customers and then gag the companies from telling anyone that they did so. Because the process is secret, and because even the companies can’t tell if specific NSLs violate the law, the process is ripe for abuse.

Let's say a social media site decides to prominently display a disclaiming banner "No National Security Letters have been sent requesting any information about your account today" to every user when they log in.

Would it be illegal for such a website to display such a banner? Would it be illegal to stop displaying it to users against whose personal data such a request has been made? If it is illegal, what's the relevant case law?

I am only asking about websites created and hosted in the United States and users physically located in the United States.

Answer 1

What you describe is essentially a Warrant Canary, which is legally murky.

From a functional point of view, it is breaking the non-disclosure requirements of the NSL by omission.

Proponents of warrant canaries would point to case law such as West Virginia State Board of Education v. Barnette and Wooley v. Maynard to suggest that the Free Speech clause of the First Amendment restricts the government from compelling speech.

New York Times Co. v. United States could also be read to prevent the prior restraint unless the existence of the NSL was successfully argued to be "crucial military information".