the fact that the three branches can only do what is in the constitution is an example of
Constitutional law
title: United States Constitution text: United States Constitution The United States Constitution is the supreme law of the United States. The Constitution, originally comprising seven articles, delineates the national frame of government. Its first three articles embody the doctrine of the separation of powers, whereby the federal government is divided into three branches: the legislative, consisting of the bicameral Congress; the executive, consisting of the President; and the judicial, consisting of the Supreme Court and other federal courts. Articles Four, Five and Six embody concepts of federalism, describing the rights and responsibilities of state governments, the states in relationship to the federal government, and the title: United States Constitution text: United States Constitution The United States Constitution is the supreme law of the United States. The Constitution, originally comprising seven articles, delineates the national frame of government. Its first three articles embody the doctrine of the separation of powers, whereby the federal government is divided into three branches: the legislative, consisting of the bicameral Congress; the executive, consisting of the President; and the judicial, consisting of the Supreme Court and other federal courts. Articles Four, Five and Six embody concepts of federalism, describing the rights and responsibilities of state governments, the states in relationship to the federal government, and the title: Article Two of the United States Constitution text: The former bestows federal legislative power exclusively to Congress, and the latter grants judicial power solely to the Supreme Court. These three articles create a separation of powers among the three branches of the federal government. In addition to separation of powers and equally important to limited government, each independent and sovereign branch also provides checks and balances on the operation and power of the other two branches. The President's executive power is subject to two important limitations. First, the President lacks executive authority explicitly granted to Congress. Hence the President cannot declare war, grant letters of marque and reprisal, title: Separation of powers under the United States Constitution text: Separation of powers under the United States Constitution Separation of powers is a political doctrine originating in the writings of Charles de Secondat, Baron de Montesquieu in "The Spirit of the Laws", in which he argued for a constitutional government with three separate branches, each of which would have defined abilities to check the powers of the others. This philosophy heavily influenced the writing of the United States Constitution, according to which the Legislative, Executive, and Judicial branches of the United States government are kept distinct in order to prevent abuse of power. This United States form of separation of title: Article One of the United States Constitution text: branches of the federal government. This separation of powers, by which each department may exercise only its own constitutional powers and no others, is fundamental to the idea of a limited government accountable to the people. The separation of powers principle is particularly noteworthy in regard to the Congress. The Constitution declares that the Congress may exercise only those legislative powers "herein granted" within Article I (as later limited by the Tenth Amendment). It also, by implied extension, prohibits Congress from delegating its legislative authority to either of the other branches of government, a rule known as the nondelegation doctrine.