From Latham Orthopedics Med. Group v. U.S.A. Corp., 2010 U.S. Dist. LEXIS 122370 (C.D. Cal. Nov. 2, 2010):

In an earlier-filed case -- Case No. EDCV 10-950-DSF (MAN) (the "950 Action") -- plaintiffs filed a complaint that is essentially identical to the instant Complaint. The 950 Action named the same two plaintiffs (Mueller and Latham) and the same five defendants as in the instant Complaint. With a few nominal variations, the text of the 950 Action complaint is identical to that of the present Complaint. While the text of both the 950 Action complaint and the instant Complaint is garbled and unintelligible, based on the defendants named in, and exhibits attached to, each pleading, it appears that, in both actions, plaintiffs are somehow complaining about and/or challenging the same federal tax assessment and levy. ***

A federal court has the inherent power "to control the disposition of the causes on its docket with economy of time and effort for itself, for counsel, and for litigants." Landis v. North American Co., 299 U.S. 248, 254, 57 S. Ct. 163, 166 (1936). District courts have inherent powers to "fashion an appropriate sanction for conduct which abuses the judicial process," and in certain cases, dismissal of a lawsuit is an appropriate sanction. Chambers v. NASCO, Inc., 501 U.S. 32, 44-45, 111 S. Ct. 2123, 2132-33 (1991); see also Ferdik v. Bonzelet, 963 F.2d 1258, 1260 (9th Cir. 1992)(district courts "have the inherent power to control their dockets" and may dismiss a case in the exercise of that power).

In the federal court system, "the general principle is to avoid duplicative litigation." Colorado River Water Conservation Dist. v. United States, 424 U.S. 800, 817, 96 S. Ct. 1236, 1246 (1976). "Plaintiffs generally have 'no right to maintain two separate actions involving the same subject matter at the same time in the same court and against the same defendant.'" Adams v. California Dep't of Health Service, 487 F.3d 684, 688 (9th Cir. 2007)(citations omitted). A district court may exercise its discretion to control its docket by dismissing a duplicative, later-filed action. Id.; see also Curtis v. Citibank, N.A., 226 F.3d 133, 138 (2d Cir. 2000)("[a]s part of its general power to administer its docket, a district court may stay or dismiss a suit that is duplicative of another federal court suit"). "Of course, simple dismissal of the second suit is [a] common disposition because plaintiffs have no right to maintain two actions on the same subject in the same court, against the same defendant at the same time." ***

Rule 41(b) of the Federal Rules of Civil Procedure grants federal district courts the authority to sua sponte dismiss actions. Link v. Wabash R. Co., 370 U.S. 626, 629-32, 82 S. Ct. 1386, 1388-89 (1961); Ferdik, 963 F.2d at 1260. In determining whether dismissal is proper, a court must weigh several factors, including: "(1) the public's interest in expeditious resolution of litigation; (2) the court's need to manage its docket; (3) the risk of prejudice to defendants; (4) the public policy favoring the disposition of cases on their merits; and (5) the availability of less drastic sanctions." Id. at 1260-61.