In PCC Airfoils, LLC v. Daugherty, No. 25-3794 (6th Cir. May 19, 2026), the Sixth Circuit declares definitively that there is no “clear and convincing” standard of proof on a Fed. R. Civ. P. 65 motion for a preliminary injunction, disaffirming a prior nonprecedential circuit decision and a string of district court opinions citing the heightened standard.
“After working for 26 years as an engineer at PCC Airfoils, Justin Daugherty accepted an offer to become the director of engineering at one of PCC’s competitors. PCC alleges that Daugherty printed several documents containing trade secrets on his way out the door. It sued and sought a preliminary injunction to prevent Daugherty from disclosing the trade secrets or working on products similar to the ones he worked on while at PCC. The district court denied the request . . . . The district court denied PCC’s motion on the ground that PCC failed to ‘establish its case’ for each of the four preliminary injunction factors by ‘clear and convincing evidence.’” Plaintiff appealed per 28 U.S.C. § 1292(a)(1).
In a brisk eight-page opinion, the Sixth Circuit reverses and remands.
“While we apply deferential review to a district court’s fact findings and its ultimate judgment about whether to grant the preliminary injunction, we treat a mistake of law as an abuse of discretion.” The panel recites the conventional four-factor test for an injunction—likelihood of success, irreparable injury to plaintiff, harm to others, and public interest—and underscores that these are not four, independent prerequisites for relief, but simply factors that are balanced by the deciding court.
“Courts, generally speaking, should engage with all four factors in a sliding-scale inquiry . . . . All of this means that a movant does not need to establish a quantum of proof, whether a preponderance or clear and convincing evidence, with respect to each factor to be eligible for preliminary relief.” The panel notes that Fed. R. Civ. P. 65 “governs the issuance of injunctive relief in federal courts,” yet “says nothing about applying a heightened standard of proof to requests for a preliminary injunction.”
“Because generalizations are dangerous when it comes to equity, and because the Supreme Court has cautioned that the clear and convincing evidence standard applies in only a few rare circumstances, E.M.D. Sales, Inc. v. Carrera, 604 U.S. 45, 47, 50–52 (2025), a court may not require every plaintiff to meet a heightened standard of proof for every preliminary injunction factor to qualify for injunctive relief. The district court erred in reaching a contrary conclusion.”
In so ruling, the panel specifically disaffirms Honeywell, Inc. v. Brewer-Garrett Co., 1998 WL 152951 (6th Cir. Mar. 23, 1998), an unpublished circuit decision that cited the elevated standard of proof.
“[Defendant also] turns to a raft of district court decisions [in this Circuit] that have applied the clear and convincing evidence standard to preliminary injunctions. But most of these cases rely on Honeywell or overread other circuit cases. At most, these district court decisions show that our circuit had not addressed this question before this year.”
“The clear and convincing evidence standard . . . had no role to play in this case. Indeed, as it pertains to the plaintiff’s likelihood of success on the merits, it seems particularly odd to require the plaintiff to prove its case by a higher standard than will be required at trial even before the parties have had the benefit of discovery.”
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