On May 6, 2019, the U.S. Court of Appeals for the First Circuit overturned its own precedent, holding that the first-to-file rule is not jurisdictional. United States v. Millennium Labs., Inc., No. 17-1106, 2019 WL 1987249, at *1 (1st Cir. May 6, 2019). The First Circuit now joins the D.C. Circuit and the Second Circuit in treating the first-to-file requirement as merely a matter of adequate pleading (see United States ex rel. Hayes v. Allstate Ins. Co., 853 F.3d 80, 86 (2d Cir.) (per curiam), cert. denied, 138 S. Ct. 199 (2017); United States ex rel. Heath v. AT&T, Inc., 791 F.3d 112, 120-21 (D.C. Cir. 2015)), widening an existing circuit split on the issue. See, e.g., United States ex rel. Wilson v. Bristol-Myers Squibb, Inc., 750 F.3d 111, 117 (1st Cir. 2014) (first-to-file rule is jurisdictional).
21 May 2019