The Constitution of United Earth was the document that regulated the function of the government of United Earth after the Traité d'Unification established United Earth's existence. Amongst the provisions of the United Earth Constitution were protections for freedom of speech and freedom of the press. (ENT novel: Beneath the Raptor's Wing)
The United Earth Constitution, along with the Andorian Pledge of Triumphant Security, the Centauri Concordium, the Statutes of Alpha III and the Fundamental Declarations of the Martian Colonies, aided in the development of the underlining principles of the Articles of the United Federation of Planets. (FASA RPG module: The Federation)