A cease and desist letter is a document sent to an individual or business to halt purportedly illegal activity ("cease") and not take it up again later ("desist"). The letter may warn that if the recipient does not discontinue specified conduct, or take certain actions, by deadlines set in the letter, that party may be sued. When issued by a public authority, a cease and desist letter, being "a warning of impending judicial enforcement", is most appropriately called a "cease and desist order".
Although cease and desist letters are not exclusively used in the area of intellectual property, such letters "are frequently utilized in disputes concerning intellectual property and represent an important feature of the intellectual property law landscape". The holder of an intellectual property right such as a copyrighted work, a trademark, or a patent, may send the cease and desist letter to inform a third party "of the right holders' rights, identity, and intentions to enforce the rights". The letter may merely contain a licensing offer, or may be an explicit threat of a lawsuit. A cease and desist letter often triggers licensing negotiations, and is a frequent first step towards litigation.
Receiving numerous cease and desist letters may be very costly for the recipient. Each claim in the letters must be evaluated, and it should be decided whether to respond to the letters, "whether or not to obtain an attorney's opinion letter, prepare for a lawsuit, and perhaps initiate [in case of letters regarding a potential patent infringement] a search for alternatives and the development of design-around technologies".
Cease and desist letters are sometimes used to intimidate recipients and can be "an effective tool used by corporations to chill the critical speech of gripe sites operators". A company owning a trademark may send such letter to a gripe site operator alleging a trademark infringement, although the actual use of the trademark by the gripe site operator may fall under a fair use exception (in compliance with, in the U.S., the protection of free speech under the First Amendment).
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