Article I of the U.S. Constitution

Article One of the United States Constitution establishes the legislative branch of the federal government, the United States Congress. The Congress is a bicameral legislature consisting of a House of Representatives and a Senate.

All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives.

Section 1 is a vesting clause that bestows federal legislative power exclusively to Congress. Similar clauses are found in Articles II and III. The former confers executive power upon the President alone, and the latter grants judicial power solely to the federal judiciary. These three articles create a separation of powers among the three 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. However, the Supreme Court has ruled that Congress does have latitude to delegate regulatory powers to executive agencies as long as it provides an "intelligible principle" which governs the agency's exercise of the delegated regulatory authority. That the power assigned to each branch must remain with that branch, and may be expressed only by that branch, is central to the theory. The nondelegation doctrine is primarily used now as a way of interpreting a congressional delegation of authority narrowly, in that the courts presume Congress intended only to delegate that which it certainly could have, unless it clearly demonstrates it intended to "test the waters" of what the courts would allow it to do.

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