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An injunction is essentially an order from a court to either do something or refrain from doing something. When a court orders a party to do something, that order is referred to as a mandatory injunction. When a court orders a party not to do something, that order is called a prohibitory injunction. Prohibitory injunctions are far more common than mandatory injunctions. In almost all cases of patent litigation, the type of injunction that will issue, assuming an injunction is appropriate, will be a prohibitory injunction, whereby the prohibition is an order to cease infringing activities.

Below is discussion of the two types of injunction normally encountered in a patent litigation: (1) a preliminary injunction, which comes at the beginning of the case and is used by the patentee to attempt to have the defendant cease activity during the pendency of the litigation; and (2) a permanent injunction, which would come at the conclusion of a patent litigation where the patent owner was able to demonstrate that the defendant had indeed engaged in infringing activity

Preliminary Injunctive Relief

It is not uncommon for a patent owner to request preliminary injunctive relief at the outset of patent litigation. This is because an enormous amount of time and energy has undoubtedly been invested in obtaining the patent, and a like commitment of resources is frequently invested post-patent in an effort to commercialize the invention. If competitors are allowed entry into the marketplace, this could significantly erode the market share of the patentee.

35 U.S.C. §283 explains that an injunction may be granted "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." The standards governing the issuance of a preliminary injunction in a patent case are no more or less stringent than in any other area of the law. In order to demonstrate entitlement to a preliminary injunction in a patent lawsuit, the requesting party must show demonstrate four things: (1) a reasonable likelihood of success on the merits; (2) irreparable harm if the injunction is not granted; (3) the balance of the hardships tipping in its favor; and (4) a tolerable effect on the public interest. The district court must balance these factors against one another and against the extent of the relief sought. While no one factor, taken individually, is necessarily dispositive, the focus of the analysis is primarily on the first two factors.

In order to establish a reasonable likelihood of success on the merits in a patent infringement case, the requesting party must show the "validity" of the patent in question and "infringement" of that patent by the accused apparatus or product. Irreparable harm may be presumed where there is a strong showing of the likelihood of success on the merits.

Permanent Injunctive Relief

Pursuant to 35 U.S.C. §283, the district court may grant a permanent injunction to prevent the violation of any right secured by patent, on such terms as the court deems reasonable. When a patent owner prevails on the merits in any patent litigation, as a general rule, a permanent injunction will issue. This type of injunction would be binding upon the parties as well as their officers, agents, servants, employees, and attorneys, and those persons in active concert or participation with them who receive actual notice of the court order by personal service or otherwise. Such an injunction also applies to subsequent actions.