Enumerated powers are the powers listed in Article 1, Section 8 and elsewhere in the U.S. Constitution that define the powers of the Congress and the government in general. These include a wide range of powers such as raising revenue, coining money, regulating commerce with other nations and between the states, establishing rules for immigration, establishing rules for bankruptcy, establishing post offices and post roads, establishing and maintaining armed forces, declaring war, and many others.
At the time of the Constitution's creation and ratification, the United States was concluding its unsuccessful experiment with the Articles of Confederation, which explicitly restricted the authority of the central government only to those enumerated powers specifically granted in the Articles, leading to an ineffectual central government that lacked even the authority to raise on its own the funds it needed to operate. It lacked the power to tax, and had to request money from the States. The new Constitution granted a much wider range of enumerated powers, and also prohibited the Congress from taking certain other actions, such as granting titles of nobility and passing retroactive legislation. It also gave Congress the right to pass any legislation necessary to implement any of the enumerated powers, or any of the other powers granted by the Constitution to any other part of the government, in what has come to be called the “necessary and proper” clause. For example, while the conduct of the decennial census is not one of the enumerated powers of Article 1, Section 8, it's mandated in Article 1, Section 2. Under the necessary and proper clause, Congress has the authority to enact the legislation necessary to carrying out the census.
The controversy over the scope of Congressional authority has been ongoing since before the Constitution was ratified. The arguments presented to the New York ratifying convention emphasized the strong nationalism that would derive from a broad, “liberal” interpretation of the Constitution, yet those presented to the Virginia Convention suggested that the central government would be limited in its scope just to those powers listed in Article 1, Section 8. Once the Constitution was ratified and then-President George Washington chaired his first cabinet meeting in 1789, he found Treasury Secretary Alexander Hamilton and Secretary of State Thomas Jefferson at odds over this very issue. For example, nowhere in the Constitution was the authority to establish or operate a bank given to the government, yet the power to coin money was specifically granted. Hamilton argued for a broad interpretation of the Constitution, saying that it was impossible for the Constitution to list every possible action the government might legitimately take, while Jefferson argued for a very strict interpretation.
The concept of the Constitution's enumerated powers is a focus of the ongoing controversy between conservatives and liberals in the U.S. Under the doctrine of “strict constructionism,” conservatives claim that Congress should limit itself to considering only those issues listed specifically in the Constitution. Liberals cite the case of McCullough v. Maryland, 17 US 316 (1819), in which the Supreme Court stated that Congress had the right to enact laws not specifically provided for in the Constitution, as long as those laws are pursuant to those express powers. Since then, two parts of the Constitution have been used as justification for a wide range of Congressional action believed by conservatives to be outside the scope of Congressional authority as defined by the Constitution. These two parts are the “commerce clause,” which gives Congress the right to regulate commerce among the states, and the Preamble, which calls for the promotion of “the general welfare.”