A cease and desist order, or "C&"D order, is a legal order that a specific person or persons stop doing a particular activity which has been identified as improper or unlawful, on pain of legal action. A cease-and-desist order, in some cases referred to as an injunction order, is issued by a judge or by certain other government agencies and carries with it the threat of legal punishment if the activity in question continues.
The precise contents and nature of a cease and desist order vary in different jurisdictions. In general, however, this is an order issued by a judge requiring that a person or persons stop an activity. Such an injunction may be issued in a wide variety of circumstances, ranging from protesters blocking progress on a logging site, to union members carrying out an illegal strike (in which case the order would require them to end the strike and either return to work or quit), to parties of a lawsuit ceasing a potentially offending activity until the lawsuit is complete. For instance, the defendant in a patent or copyright lawsuit might be ordered to stop distributing an allegedly offending piece of literature, video, or computer software pending the outcome of the trial. In general, the order would apply to a civil matter over which the court has jurisdiction; if the offending behaviour were criminal, one would expect criminal charges to be laid instead. Where the order is intended to prevent harassment or assault, it may take the form of a separate injunction called a restraining order (or sometimes a protection order).
In certain states and countries, government agencies with special regulatory powers are also allowed to issue cease and desist orders relating to their areas of activity. In the United States, for instance, the Securities and Exchange Commission (SEC), which is responsible for regulating the stock markets and certain public affairs of publicly traded companies, has the power to issue orders requiring immediate cessation of illegal activity, along with returning (known as "disgorging") any profits gained through the illegal activity.
Note that a cease and desist order, as described above, is different from a cease and desist letter. A cease and desist letter is simply a request to stop an activity, and carries no inherent legal force. Instead, a cease-and-desist letter usually is accompanied by a threat that if the activity is not stopped, there will be a lawsuit to make it stop. Cease-and-desist letters can be sent by anyone, and do not require review or approval by a judge or any other government agency. Today, one of the most common types of cease-and-desist letters are demands by copyright-holders that alleged copyright violations (such as sharing a video on an online website) cease. However, they can also be issued in cases of harassment, libel, and other disputes.
If you have questions about requesting, receiving, or responding to a cease and desist order, you should always take these concerns to a qualified lawyer, who can give you professional legal advice tailored to your particular situation.