Terrorism as recently practiced in Paris and the emergence of the Islamic State in the Middle East make it becomes imperative to create a new legal superstructure and international policy to address these new issues, that is, the structuring of a world government because no great power will be able to defeat him for more power which has, or act in coalition with other great powers. The preservation of peace is the first mission of every new form of world government. It would aim to defend the general interests of the planet making it compatible with the interests of each nation. The world government would also work as mediator in international conflicts and build consensus among all nation states to make every national state respects the rights of its citizens, and seek to prevent the spread of global systemic risks. Actions to be a global governance was objective of Nations Covenant in 1815, the League of Nations in 1920 and of the United Nations in 1945 that were in vain because the great powers chose to impose their will on the world.