Approximately the entire 20th century, the Panama Canal (including a strip of land bordering the canal known as the ‘canal zone’) was essentially controlled by the United States, a control which included the primary responsibility for its defence. With the onset of the new millennium, however, the canal reverted to exclusive Panamanian control. This contribution will briefly recall the legal basis of this watershed which dates from 1977 and indicate if the United States retains any residual powers as regards the Panama Canal in particular its defence.