Manufacturing companies sometimes try to use patent infringement lawsuits to protect their market shares by attempting to obtain permanent injunctions against their competitors’ infringing products. In 2006, the Supreme Court ineBay v. MercExchange, 547 U.S. 388 (2006), made the job of qualifying for a permanent injunction more difficult, but still not impossible. After eBay, patent owners cannot simply rely on findings of infringement and no invalidity of the patent-in-suit to carry them over the goal line. The presumption of irreparable harm flowing from each and every patent infringement, which automatically resulted in injunctions pre-eBay, is no more. Now patent owners have to prove irreparable harm like everybody else who is seeking equitable relief.

The strongest case of irreparable harm is presented by a patent owner who has a product of its own which practices the infringed patent and directly competes with the infringing product in a two-supplier market. The patent owner has to show that the customers can essentially buy the same product from each of them. The more the facts in a case differ from this injunction-friendly scenario, the harder it is to prove irreparable harm and get an injunction.

A four-factor test now governs the grant of permanent injunctions...