Nation Magazine v. United States Department of Defense
In 1990, the United States Department of Defense implemented press pools so they could control and monitor the press during the Gulf War. The competition into the press pools was intense and if a publication wasn't a member of the pool, they were unable to gain access to the warzones and could not fully cover the war.
Source: Wikipedia — Nation Magazine v. United States Department of Defense (CC BY-SA 4.0)