Prior restraint

Prior restraint (also referred to as prior censorship or pre-publication censorship) is censorship imposed, usually by a government or institution, on expression, that prohibits particular instances of expression. It is in contrast to censorship that establishes general subject matter restrictions and reviews a particular instance of expression only after the expression has taken place. In some countries (e.g., United States, Argentina) prior restraint by the government is forbidden, subject to exceptions (such as classifying certain matters of national security), by their respective constitutions. Prior restraint can be effected in a number of ways. For example, the exhibition of works of art or a movie may require a license from a government authority (sometimes referred to as a classification board or censorship board) before it can be published, and the failure or refusal to grant a license is a form of censorship as is the revoking of a license. It can take the form of a legal injunction or government order prohibiting the publication of a specific document. Sometimes, a government or other party becomes aware of a forthcoming publication on a particular subject and seeks to prevent it: to halt ongoing publication and prevent its resumption. These injunctions are considered prior restraint because potential future publications are stopped in advance. It can also take the form of a (usually secret) policy imposed by a commercial corporation upon its employees, requiring them to obtain written permission to publish a given written work, even one authored outside of work hours produced using their own computing resources.