You might think that Rep. Devin Nunes (R-Calif.), the Ranking Member of the House Intelligence Committee, would be too busy to file baseless defamation lawsuits against anonymous Twitter accounts. But you’d be wrong.

Last year, Rep. Nunes sued a number of people who were mean to him online, including the Twitter parody accounts Devin Nunes’ Mom and Devin Nunes’ Cow. Now, he’s trying to unmask the Cow by subpoenaing the author’s identity from a local law firm. The ACLU and Public Citizen have filed a friend-of-the-court brief urging the court to block Nunes’ subpoena because it violates the First Amendment right to anonymous speech.

From Sam Adams to Mark Twain, Americans throughout history have used pseudonyms to criticize public officials. People adopt pseudonyms for a number of different reasons, such as protecting privacy and preventing official retaliation. The Supreme Court has made clear that “an author’s decision to remain anonymous, like other decisions concerning omissions or additions to the content of a publication, is an aspect of freedom of speech protected by the First Amendment.”

To protect anonymous speech, courts require defamation plaintiffs to satisfy a number of criteria before allowing them to use subpoenas and other discovery tools to unmask anonymous speakers. As particularly relevant here, a plaintiff must demonstrate that the defendant’s statements are plausibly defamatory (i.e., not protected opinion, parody, or political rhetoric) and produce evidence showing that the defendant’s statements were actually false. These requirements prevent plaintiffs from using meritless defamation claims as a vehicle to identify anonymous critics for purposes of retaliation, while allowing plaintiffs with legitimate claims to proceed. As we argue in our friend-of-the-court brief, these safeguards are not just good policy – they’re required by the First Amendment.