Article I of the U.S. Constitution creates Congress and gives it all federal lawmaking power. The Framers put the legislative branch first in the document on purpose, signaling that an elected body, not a single executive, should sit at the center of national government. Everything the Constitution says about Congress flows from that choice: two chambers with different rules, a defined list of powers, hard limits on what those powers can do, and a set of tools for checking the President and the courts.
Two Chambers With Different Rules
Congress is bicameral. A bill has to clear two separate chambers, each with its own membership, term length, and method of representation, before it can go anywhere.
The House of Representatives
House members must be at least 25 years old, a U.S. citizen for at least seven years, and a resident of the state they represent when elected. They serve two-year terms, so every seat is on the ballot every general election cycle. That short term keeps representatives close to public opinion.
House seats are apportioned among the states by population, recalculated after each ten-year census. The 435 total seats shift toward states that grow and away from states that shrink, so more populous states carry proportionally more weight in the chamber.
The Senate
Senators face higher thresholds: at least 30 years old, a U.S. citizen for at least nine years, and a resident of the state they represent. Terms run six years and are staggered, so roughly one-third of the Senate is up for election every two years. The Framers designed the Senate as a more deliberative body, and the longer, overlapping terms are meant to buffer it from short-term political swings.
Every state gets two senators regardless of population. Wyoming and California each send two. This equal representation was the compromise that convinced smaller states to ratify the Constitution.
The Vice President serves as President of the Senate but votes only to break a tie. Day-to-day presiding usually falls to the president pro tempore or another designated senator.
What Congress Can Do: The Enumerated Powers
Article I, Section 8 lists Congress’s specific powers. They cover the money, the military, commerce, and the machinery of the federal government.
Taxing, Spending, and Borrowing
Congress can levy taxes to pay debts and fund the national defense and general welfare. It can borrow on the credit of the United States, which is the constitutional basis for Treasury bonds and the national debt. And no federal money can be spent without a congressional appropriation. That single restriction gives Congress direct control over every dollar the government uses.
There is also a structural rule about where tax bills start. All bills that raise revenue must originate in the House. The Senate can amend a revenue bill once the House passes it, but it cannot introduce one. The reasoning was that the chamber closest to voters should have first say over taxation.
Regulating Commerce
The Commerce Clause gives Congress authority over trade with foreign nations, among the states, and with Native American tribes. Because so much modern economic activity crosses state lines, this one clause has become the constitutional foundation for a wide range of federal regulation, from labor rules to environmental standards. Centralizing commerce power in Congress also blocks a patchwork of conflicting state trade rules.
War Powers and the Military
Only Congress can declare war. It also raises and funds armies, maintains a navy, and sets rules governing the armed forces. Military funding appropriations are capped at two-year terms, which forces Congress to reauthorize spending regularly instead of bankrolling a standing army indefinitely. Civilian control runs through the elected legislature.
Money, Mail, Naturalization, and Bankruptcy
Congress alone can coin money and set its value, establish post offices and postal routes, and write uniform rules for naturalization and bankruptcy. The uniformity requirement means those systems have to work the same way in every state, which prevents jurisdiction-shopping from undermining national standards.
Patents and Copyrights
Section 8 also lets Congress grant authors and inventors exclusive rights to their works and discoveries for limited periods. That clause is the constitutional foundation of the entire federal patent and copyright system. Temporary monopolies encourage creation, and the works eventually enter the public domain.
Lower Federal Courts
The Constitution itself creates only the Supreme Court. Every federal district court and circuit court of appeals exists because Congress chose to create it. That authority also lets Congress reshape the federal judiciary’s structure, including the number of judges and the jurisdiction of each court.
The Necessary and Proper Clause
The last clause of Section 8 lets Congress pass any law “necessary and proper” for carrying out its listed powers. It is sometimes called the Elastic Clause, and it allows the legislature to adapt without a constitutional amendment every time circumstances change.
The 1819 case McCulloch v. Maryland set how far the clause reaches. Congress had chartered a national bank, and Maryland argued no enumerated power authorized it. Chief Justice John Marshall disagreed. Because Congress could tax, borrow, and regulate commerce, creating a bank was a legitimate means of executing those powers. The principle still governs: if the end is within an enumerated power and the means is not prohibited by the Constitution, Congress can act.
The clause has real limits. It is not a standalone grant of authority. Every law passed under it has to connect to some enumerated power. It stretches the toolkit, not the jurisdiction.
What Congress Cannot Do
Article I, Section 9 draws hard lines around congressional power. These prohibitions protect individual rights and keep the legislature out of areas the Framers considered dangerous.
Habeas Corpus
Congress cannot suspend the writ of habeas corpus, which lets a person in custody challenge that detention before a judge. The only exception is during rebellion or invasion when public safety requires it. Without this protection, the government could hold people indefinitely without judicial review.
Bills of Attainder and Ex Post Facto Laws
Congress cannot pass a bill of attainder, which is a legislative act declaring someone guilty of a crime without a trial. Congress is a lawmaking body, not a court. Ex post facto laws are also forbidden. If conduct was legal when you did it, Congress cannot retroactively criminalize it and punish you.
Export Taxes and the Appropriations Rule
Congress cannot tax goods exported from any state. And no money can leave the Treasury without a legal appropriation, with regular public statements of receipts and expenditures required. Every dollar spent has a paper trail back to a congressional authorization.
Titles of Nobility and Foreign Gifts
The United States cannot grant titles of nobility. No federal officeholder may accept a gift, title, or payment from a foreign government without Congress’s consent. The clause targets both aristocratic hierarchy and foreign influence.
How a Bill Reaches the President
Once both chambers pass identical versions of a bill, it goes to the President, who has three options. Signing it makes it law. Vetoing it sends the bill back to the originating chamber with written objections, and Congress can override the veto only if two-thirds of each chamber votes to do so, with every vote recorded by name. That threshold is high, and most vetoes stick.
If the President neither signs nor vetoes within ten days (Sundays excluded) while Congress is in session, the bill becomes law without a signature. But if Congress adjourns during that window and prevents the bill’s return, the bill dies. That is a pocket veto, and there is no override.
Powers Beyond Lawmaking
Congress holds several authorities that have nothing to do with passing legislation. These are the direct checks on the executive and the judiciary.
Impeachment
The House alone can impeach federal officials, including the President. Impeachment works like an indictment: a simple majority of the House approves articles of impeachment, and a committee of House members prosecutes the case in the Senate. The Senate is the trial court. When a president is on trial, the Chief Justice of the United States presides. Conviction requires a two-thirds vote of senators present, and the penalty is removal from office. The Senate may also vote separately to bar the convicted official from holding any future federal position.
Treaties and Appointments
The President negotiates treaties, but no treaty takes effect unless two-thirds of senators present approve it. The Senate also confirms the President’s nominees for federal judges, cabinet members, ambassadors, and other senior officials. A nominee who cannot get Senate approval does not take office, which gives Congress real influence over both the executive branch and the federal courts.
How Congress Governs Itself
Each chamber sets its own procedural rules, which is why the House and Senate operate so differently. A majority of each chamber is a quorum. Without it, business cannot proceed, though a smaller number can adjourn from day to day and compel absent members to show up.
Either chamber can discipline members for disorderly behavior. With a two-thirds vote, either chamber can expel a member outright. Expulsion is rare because the threshold is so high, but the power is there.
Article I, Section 6 protects legislative debate itself. Members cannot be questioned in any other place for anything they say during legislative activity. A senator or representative can speak on the floor without facing a lawsuit or criminal prosecution over those words. The point is to keep the executive branch from intimidating legislators through the threat of arrest or prosecution. Members also have a limited privilege from arrest while traveling to and from sessions, except for treason, felony, or breach of the peace.
Congress and Constitutional Amendments
Article V gives Congress a central role in changing the Constitution itself. Two-thirds of both the House and Senate can propose an amendment. The threshold is two-thirds of members present, assuming a quorum, not two-thirds of total membership. Alternatively, if two-thirds of state legislatures request it, Congress must call a convention for proposing amendments. That convention path has never been used, and much about how it would work remains unsettled.
Once an amendment is proposed, Congress decides how the states will ratify it: by three-fourths of state legislatures or by conventions in three-fourths of the states. Congress can also set a ratification deadline, and the Supreme Court confirmed in Dillon v. Gloss (1921) that reasonable time limits are permissible. If the deadline passes without enough states ratifying, the amendment dies and the whole proposal process starts over.