Federal agents with Homeland Security Investigations tried to track down Rochester resident David Streever last month and give him a warning notice alleging that he had potentially violated the law when he wrote a harsh email months earlier to the former head of U.S. Immigration and Customs Enforcement.

Now a lawsuit filed by the nonprofit Foundation for Individual Rights and Expression on Monday in federal court in Washington, D.C. argues Streever’s January email was protected speech and the federal agents’ and their superiors violated Streever’s First Amendment rights.

The three-paragraph note compared Lyons to a Nazi and predicted that Lyons would be tormented by his own conscience. It has the subject line, “What’s next.”

Five months later, on June 23, two HSI agents rang the doorbell of Streever’s Rochester home and then left a document with Streever’s wife for him to sign. It was labeled “WARNING NOTICE” and “YOU MAY BE IN VIOLATION OF FEDERAL LAW,” and described federal laws that make it a crime to threaten federal officials. The notice said ICE’s Office of Professional Responsibility had identified an email to Lyons that may violate federal law and the office “is requesting that you promptly remove and/or discontinue the aforementioned behavior.”