The Republican and Democratic Party conventions later this summer will probably witness the mass arrest of many American citizens assembling to exercise their First Amendment rights. Mass arrests accompanied the Republican conventions held in New York in 2004, when 900 people were busted, and in St. Paul in 2008 when 300 were detained, including 30 journalists.
A political convention is designated a National Special Security Event (NSSE), a category of state security originally established by President Clinton through a classified 1998 directive. NSSEs also include the Olympics, the Super Bowl and gatherings of world leaders like the G20 or NATO summits. An event receiving a NSSE designation gives federal and local law enforcement wide discretion, often leading them to treat protesters as potential terrorists and threats to national security.