Separation of Powers
The Constitution divides the federal government into three branches: a legislature that makes the laws, an executive that enforces them, and a judiciary that interprets them. Each branch has tools to check the others.
The separation of powers is the framework that organizes the federal government. Article I vests legislative power in Congress. Article II vests executive power in the President. Article III vests judicial power in the Supreme Court and such lower courts as Congress establishes. The framers drew the idea from the writings of Montesquieu and from their own bitter experience with both monarchical overreach and the legislative tyranny of some state governments during the Confederation period. They did not separate the powers cleanly. Each branch shares some functions of the others to check overreach. The President signs or vetoes legislation. The Senate confirms appointments and ratifies treaties. The Supreme Court reviews the constitutionality of statutes and executive actions. Congress can override vetoes, impeach officials, and structure the courts. James Madison wrote in Federalist 47 that "the accumulation of all powers, legislative, executive, and judiciary, in the same hands, whether of one, a few, or many, and whether hereditary, self-appointed, or elective, may justly be pronounced the very definition of tyranny." Modern separation-of-powers questions arise constantly. Executive orders that effectively make new policy without congressional action raise the question of which branch is acting. Programs like DACA have been challenged on these grounds. Agency rulemaking under broad statutory delegations has drawn renewed Supreme Court attention in recent decades. Wars conducted without explicit congressional authorization stretch the war power across both political branches. The separation of powers is not a tidy diagram. It is an ongoing negotiation among three coequal branches, conducted within the boundaries of the constitutional text, that has held for more than two centuries.