The Indian Constitution is the largest written constitution in the world, with a federal structure and a parliamentary system of government. It provides for a single citizenship, a three-tier system of government, and an integrated judiciary. The Constitution grants fundamental rights to citizens and also outlines the directive principles of state policy. The Indian Parliament has the power to amend the Constitution, subject to certain limitations. The President of India has emergency powers that can be invoked in times of war, internal disturbance, or financial crisis.