eBay Inc. v. MercExchange — Four-Factor Equity Test Governs Permanent Injunctions in Patent Cases

Background

MercExchange held a portfolio of patents on electronic marketplace technology, including a business method patent covering features central to how eBay operated its online auction platform — specifically, the ability to make immediate purchases at a fixed price (eBay’s “Buy It Now” feature). MercExchange had tried to license its patents to eBay without success. It then sued for infringement.

A jury found MercExchange’s patents valid and infringed and awarded approximately $35 million in damages. MercExchange then sought a permanent injunction requiring eBay to stop using the patented technology. The district court denied the injunction, noting that MercExchange was a patent licensing company that did not itself practice the invention and had indicated willingness to license rather than exclude. The Federal Circuit reversed, applying its long-standing general rule that upon a finding of infringement, permanent injunctions should issue as a matter of course absent exceptional circumstances.

The Supreme Court granted certiorari to determine whether the traditional test for injunctive relief applied to patent cases.

The Court’s Holding

Justice Thomas, writing for a unanimous Court, held that the traditional four-factor test for permanent injunctive relief applies in patent cases just as in any other area of law. A plaintiff seeking a permanent injunction must demonstrate: (1) that it has suffered an irreparable injury; (2) that remedies available at law, such as monetary damages, are inadequate to compensate for that injury; (3) that considering the balance of hardships between the plaintiff and defendant, a remedy in equity is warranted; and (4) that the public interest would not be disserved by a permanent injunction.

The Court rejected both of the categorical approaches below. The Federal Circuit’s near-automatic rule in favor of injunctions upon a finding of infringement was wrong: it essentially collapsed the four-factor test by treating a finding of infringement as sufficient by itself. But the Court also rejected the district court’s apparent suggestion that patentees who do not practice their inventions or who are willing to license can categorically be denied injunctions. Some of the most important historic uses of patent rights — by individual inventors, universities, and small companies — involve entities that license rather than manufacture. Neither the statute nor equity principles support a categorical rule against relief for such patentees.

Justice Kennedy’s concurrence, joined by three Justices, added important guidance: courts should be alert to the possibility that the threat of an injunction may be used as a bargaining chip by patent holders seeking outsized licensing fees, particularly for patents that are a small component of a larger product.

Key Takeaways

• Permanent injunctions in patent cases are not automatic upon a finding of infringement; courts must apply the traditional four-factor equitable test.
• Patent holders who do not practice their inventions (non-practicing entities or “NPEs”) are not categorically barred from obtaining injunctions, but their non-practicing status is relevant to the irreparable harm analysis.
• Courts must make individualized findings on each of the four factors; categorical rules — in either direction — are impermissible.
• Willingness to license may weigh against a finding of irreparable injury, since licensing fees may adequately compensate the patentee.

Why It Matters

eBay v. MercExchange is one of the most consequential patent decisions of the past two decades. Before this ruling, winning a patent case in the Federal Circuit came with a near-guarantee of an injunction — a powerful lever that patent holders, including so-called “patent trolls,” could use to force high settlements from defendants who feared being shut down entirely. The decision eliminated that guarantee.

After eBay, courts routinely deny injunctions to non-practicing entities, finding that damages are an adequate remedy since NPEs do not compete in the market and suffer no competitive harm from continued infringement. For operating companies that compete head-to-head, injunctions remain more available. The decision reshaped the economics of patent litigation and weakened the leverage that patent assertion entities could extract in settlement negotiations, while preserving meaningful injunctive relief for genuine competitors.