Like a hard brake before a pileup, this is a written warning telling someone to stop doing something now and not start again. Legally, a cease and desist letter is usually sent by a lawyer or rights holder to accuse a person or business of unlawful conduct - often trademark infringement, copyright infringement, patent infringement, defamation, or misuse of trade secrets - and to demand that the conduct end before a lawsuit gets filed. It is not a court order. It carries no automatic legal force by itself. But it is a serious shot across the bow, and ignoring it can get expensive fast.

In practice, these letters matter because they put the dispute on record. They can demand that someone pull a product, remove online content, preserve evidence, pay money, or confirm in writing that the conduct has stopped. In IP fights, they often mention federal laws like the Lanham Act for trademarks or the Copyright Act of 1976. They can also shape whether a later claim looks willful, which can increase damages.

For an injury claim, the effect is usually indirect but real. If accident photos, medical records, business branding, or case-related content are being used without permission, a cease and desist letter can force that use to stop and help protect evidence, reputation, or settlement leverage. Sending one carelessly, though, can backfire if the accusation is weak.