eBay Inc. v. MercExchange, L.L.C.
eBay ended the Federal Circuit's general rule that a permanent injunction follows almost automatically from a finding of patent infringement. The Supreme Court restored the traditional four-factor equitable test, requiring patentees to establish irreparable injury, inadequate legal remedy, a favorable balance of hardships, and the public interest before obtaining permanent injunctive relief.
Holding
The Supreme Court held that the traditional four-factor test for permanent injunctions applies to disputes arising under the Patent Act. A patentee seeking a permanent injunction must demonstrate (1) that it has suffered an irreparable injury; (2) that remedies available at law are inadequate to compensate for that injury; (3) that, considering the balance of hardships between the parties, an equity is warranted; and (4) that the public interest would not be disserved by a permanent injunction. The Court rejected the Federal Circuit's "general rule" that an injunction issues absent exceptional circumstances and likewise rejected the district court's categorical denial of injunctive relief based on the patentee's status.
Procedural posture and facts
MercExchange held patents on methods for online auction-style sales. It sued eBay, alleging that eBay's "Buy It Now" feature infringed. A jury found infringement and validity and awarded damages. MercExchange moved for a permanent injunction. The Eastern District of Virginia denied the motion, citing among other things MercExchange's willingness to license, its lack of commercial activity practicing the patents, and concerns about whether MercExchange would suffer irreparable harm absent an injunction.
The Federal Circuit reversed, applying its long-standing "general rule" that courts will issue permanent injunctions against patent infringement absent exceptional circumstances. MercExchange, L.L.C. v. eBay, Inc., 401 F.3d 1323 (Fed. Cir. 2005). The Supreme Court granted certiorari to address whether the Federal Circuit's general rule departed from the traditional principles of equity.
The Court's reasoning
Justice Thomas, writing for a unanimous Court, kept the analysis brief. Two fundamental points framed the opinion.
Patent Act preserves traditional equity
Section 283 of the Patent Act provides that courts "may grant injunctions in accordance with the principles of equity to prevent the violation of any right secured by patent, on such terms as the court deems reasonable." 35 U.S.C. § 283. The statute speaks of equitable principles; it does not authorize a categorical rule for or against injunctions. The Court analogized to the Copyright Act, which uses similar permissive language and which the Court had long treated as preserving traditional equitable analysis. There is no reason to read the Patent Act differently.
Both lower courts erred
The district court erred in suggesting that a patentee that does not commercially practice its invention or that is willing to license is categorically ineligible for injunctive relief. The Patent Act does not condition the right to exclude on commercial practice; the statute expressly contemplates that patentees may license their patents.
The Federal Circuit erred in the opposite direction. Its "general rule" that an injunction issues absent exceptional circumstances effectively converted the equitable inquiry into an administrative one in which the patentee almost always prevailed. That, too, departed from traditional equity.
The Court's instruction was simple: apply the four traditional factors as one would in any equitable case, on the facts before the court, without categorical thumbs on either side of the scale. The Court vacated and remanded for the district court to apply the proper test in the first instance.
Concurrences
Two concurrences elaborated. Chief Justice Roberts, joined by Justices Scalia and Ginsburg, emphasized the historical practice: from the early days of the patent system, courts had granted injunctions in the vast majority of cases where infringement was found. That practice should weigh in the equitable analysis. The Chief Justice's concurrence suggested that, when applying the traditional test, district courts should not write on a blank slate.
Justice Kennedy, joined by Justices Stevens, Souter, and Breyer, took a different view. He noted that the patent landscape had changed: an "industry has developed in which firms use patents not as a basis for producing and selling goods but, instead, primarily for obtaining licensing fees." For such patentees, "an injunction, and the potentially serious sanctions arising from its violation, can be employed as a bargaining tool to charge exorbitant fees." Kennedy's concurrence flagged that the four-factor analysis should be sensitive to those realities. The Kennedy concurrence is widely cited for the proposition that non-practicing entities (NPEs) face a steeper path to injunctive relief.
The framework eBay produced
After eBay, every motion for a permanent injunction in a patent case applies the four-factor test:
- Irreparable injury: The patentee must show that the harm cannot be adequately remedied by damages. Lost market share, price erosion, lost sales of complementary products, loss of reputation or goodwill, and loss of research-and-development incentives are common categories.
- Inadequacy of legal remedies: The patentee must show why money damages — including any reasonable royalty for ongoing infringement — would not make it whole.
- Balance of hardships: The court weighs the harm to the patentee from continued infringement against the harm to the infringer from being enjoined, including effects on employees, customers, and design-around efforts.
- Public interest: The court considers whether enjoining the accused product disserves the public — for example, by depriving consumers of an essential medicine or critical infrastructure.
The framework also affects relief short of full injunction. Courts may craft narrower equitable relief, including sunset periods, design-around windows, and ongoing royalty orders that function as judicial alternatives to a full injunction. When the four factors weigh against an injunction, an ongoing royalty under § 283 may issue.
Subsequent application
The most visible effect of eBay was on patentees who do not practice their patents. The Kennedy concurrence has loomed large: courts evaluating injunctions sought by NPEs frequently find irreparable harm absent and damages adequate, because a willing-licensor patentee can typically be made whole by a royalty. By contrast, operating-company patentees that compete head-to-head with infringers — especially in pharmaceuticals, medical devices, and other markets with strong head-to-head competition — continue to obtain injunctions when they prove harm to their market position.
eBay also reshaped settlement dynamics. Before eBay, a patentee that proved infringement could often extract a settlement reflecting the threat of a near-automatic injunction. After eBay, settlement values have moved closer to expected damages awards, particularly for NPE-driven cases. Litigation in the Eastern District of Texas, the Western District of Texas, and Delaware reflects the post-eBay equilibrium: damages-driven cases with ongoing royalties as the practical remedy in many NPE matters.
The framework has been extended beyond permanent injunctions. The Federal Circuit applied eBay-style equitable analysis to preliminary injunctions in Winter v. Natural Resources Defense Council, Inc., 555 U.S. 7 (2008), which separately confirmed that the four-factor test governs in non-patent contexts as well. Today, every form of equitable relief in patent cases — from temporary restraining orders to permanent injunctions to ongoing royalty orders — proceeds through the same four-factor lens.
eBay also influenced the use of administrative bans through the U.S. International Trade Commission. The ITC issues exclusion orders rather than injunctions, and Section 337 governs through a separate "public interest" inquiry rather than the Patent Act. The differential remedy — exclusion orders without an eBay-style equity test — has made the ITC an attractive alternative forum for patentees who would struggle to obtain injunctive relief in district court.
Open questions and pressure points
Three pressure points remain. First, the line between "willing licensor" and "irreparably harmed" practicing entity is fact-bound and the Federal Circuit's case law on the proper nexus between the infringing feature and the alleged harm has continued to develop. A patentee that proves a feature drives demand has a stronger irreparable-harm case than one that proves only general competition.
Second, the post-eBay landscape has shifted relief toward ongoing royalties. The Federal Circuit has approved ongoing royalty orders under § 283 where a permanent injunction is denied, but the methodology for setting the rate — whether it should equal, exceed, or relate to the jury's reasonable-royalty verdict — remains contested.
Third, the public-interest factor has taken on weight in pharmaceutical and standard-essential-patent cases. Courts have considered patient access, public health, and the role of standardized technologies in deciding whether to enjoin infringement. The interaction between eBay and FRAND commitments on standard-essential patents, in particular, is a continuing source of doctrine.
Finally, the Kennedy concurrence's NPE skepticism continues to influence outcomes even though it is not the majority opinion. Whether it should — and how to define the relevant categories of patentee — is part of the ongoing debate over the patent system's structure.
Citation and record
Formal citation: eBay Inc. v. MercExchange, L.L.C., 547 U.S. 388 (2006).
Below: MercExchange, L.L.C. v. eBay, Inc., 401 F.3d 1323 (Fed. Cir. 2005), reversing the district court's denial of a permanent injunction.
Author: Justice Thomas for a unanimous Court. Argued March 29, 2006; decided May 15, 2006.
Vote alignment: 9-0. Concurrences by Chief Justice Roberts (joined by Scalia and Ginsburg) and by Justice Kennedy (joined by Stevens, Souter, and Breyer).
See also
- Permanent injunctionsThe doctrinal home of the eBay four-factor test.
- Reasonable royaltyThe default damages remedy and the basis for ongoing royalty orders.
- Lost profitsAn alternative damages measure especially relevant for practicing-entity patentees.
- ITC Section 337 investigationsThe administrative exclusion-order remedy that operates outside eBay.
- Halo Electronics, Inc. v. Pulse Electronics, Inc.Enhanced damages under § 284 — a separate post-judgment remedy.
- Octane Fitness, LLC v. ICON Health & Fitness, Inc.Attorney-fee awards under § 285 — a related discretionary remedy.
- Title 35 reference35 U.S.C. § 283 governs injunctive relief.
Last reviewed: 2026