In a thorough exploration of the Supreme Court's interpretation of the political power distributed by the Constitution, Epstein and Walker explain and analyze such essential concepts as separation of powers and federalism, as well as the authority to tax, spend, conduct war, regulate commerce, and limit rights to property and contracts. This revised volume includes both recent and important rulings on limits to federal power, and thoughtfully examines the impact of national emergencies, terrorism, and the war in Iraq on the government's capacity to act in the interests of national security.