The United States Constitution places clear limits on the powers of Congress, and understanding which action Congress cannot perform is essential for anyone studying American government. Now, while the legislative branch holds broad authority to make laws, declare war, and control the federal budget, the Constitution explicitly forbids certain legislative acts that would violate individual rights, upset the balance of powers, or undermine the rule of law. This article explores those prohibited actions in depth, explains the constitutional basis for each, and answers common questions about their practical implications.
Introduction
The Constitution’s Article I establishes Congress as a bicameral body composed of the House of Representatives and the Senate. In real terms, these restrictions are designed to protect civil liberties, preserve the separation of powers, and see to it that the federal government operates within a framework of limited authority. Its enumerated powers include the ability to levy taxes, regulate commerce, and provide for the common defense. Even so, the same article also contains specific prohibitions that prevent Congress from overstepping its bounds. By examining the text of the Constitution, relevant judicial interpretations, and historical examples, we can identify precisely which actions Congress is barred from performing.
Prohibited Legislative Actions
1. Enacting Ex Post Facto Laws
What it is: An ex post facto law is a statute that makes an act criminal after the fact or increases the punishment for a crime committed before the law’s passage Simple, but easy to overlook. Simple as that..
Constitutional basis: Article I, Section 9, Clause 3 states that “No State shall… pass any... ex post facto law.” The Supreme Court has interpreted this prohibition to apply to Congress as well, because the clause was intended to protect both states and the federal government from similar abuses But it adds up..
Why it matters: Allowing Congress to retroactively criminalize conduct would threaten the principle of nullum crimen sine lege (no crime without law) and could be used to punish political opponents or target specific groups Practical, not theoretical..
Example: In United States v. Butler (1936), the Court struck down a federal tax law that effectively imposed penalties for activities that were not already illegal, emphasizing that Congress cannot create new criminal penalties without prior statutory definition Turns out it matters..
2. Passing Bills of Attainder
What it is: A bill of attainder is a legislative act that punishes a specific individual or a narrow class of persons without a judicial trial.
Constitutional basis: Article I, Section 9, Clause 3 also bars Congress from passing bills of attainder Simple, but easy to overlook. Still holds up..
Why it matters: This prohibition reinforces the separation of powers by ensuring that the legislative branch does not usurp the judicial function. The Supreme Court has repeatedly held that bills of attainder violate due process guarantees.
Example: In United States v. Lovett (1895), the Court invalidated a law that barred specific individuals (former Confederate officials) from receiving government employment, labeling it a bill of attainder.
3. Suspending the Writ of Habeas Corpus
What it is: The writ of habeas corpus is a legal mechanism that requires the government to justify the detention of an individual.
Constitutional basis: Article I, Section 9, Clause 2 permits the suspension of habeas corpus “when in Cases of Rebellion or Invasion the public Safety may require it.”
Why it matters: While the Constitution allows suspension under extreme circumstances, it does not grant Congress an unrestricted power to do so. The suspension must be justified by actual rebellion or invasion, and any such action must be consistent with the due process rights of individuals.
Example: During the Civil War, President Lincoln suspended habeas corpus in certain military districts, a move that sparked legal debates about the limits of congressional and executive authority.
4. Impairing the Obligation of Contracts
What it is: This refers to legislation that retroactively alters or nullifies private contracts.
Constitutional basis: Article I, Section 10 (applicable to the states) prohibits any state from passing laws that impair contract obligations. Although the clause is directed at the states, the Supreme Court has interpreted the Fifth Amendment’s Due Process Clause as extending similar protection to the federal government Practical, not theoretical..
Why it matters: The protection of contractual rights promotes economic stability and reliance on private agreements.
Example: In Home Building & Loan Association v. Blaisdell (1934), the Court upheld a state law that temporarily altered mortgage contracts during the Great Depression, showing that even the federal government must be cautious when interfering with contractual obligations Worth keeping that in mind..
5. Altering the Constitution Without the Proper Procedure
What it is: Changing the text of the Constitution itself.
Constitutional basis: Article V outlines a rigorous amendment process that requires proposal by two‑thirds of both houses of Congress or a constitutional convention called by two‑thirds of the states, followed by ratification by three‑fourths of the states Easy to understand, harder to ignore..
Why it matters: This safeguard ensures that any amendment reflects broad consensus rather than a fleeting majority in Congress That alone is useful..
Example: Congress cannot unilaterally rewrite the Bill of Rights; any change must follow the amendment procedure, preserving the document’s stability.
Other Notable Limitations
a. No Declaration of War Without Proper Authority
While Congress does have the power to declare war (Article I, Section 8), it cannot unilaterally engage in military actions that bypass the constitutional process. The War Powers Resolution of 1973 further clarifies that the President may only commit forces for limited periods without explicit congressional authorization But it adds up..
b. No Power to Impose Direct Taxes Without Apportionment
The original Constitution required direct taxes to be apportioned among the states based on population (Article I, Section 9, Clause 4). Although the Sixteenth Amendment later removed this restriction, the original clause illustrates the framers’ concern about concentrated fiscal power Simple, but easy to overlook..
c. No Ability to Change the Size of the Supreme Court or Federal Judiciary
Article I grants Congress the power to “ordain and establish” lower federal courts, but it cannot alter the jurisdiction or size of the Supreme Court in a way that undermines judicial independence. Attempts to “pack” the Court or strip its authority would likely violate the separation of powers The details matter here..
Counterintuitive, but true.
Conclusion
The short version: the Constitution expressly forbids Congress from performing several critical actions: enacting ex post facto laws, passing bills of attainder, suspending the writ of habeas corpus outside the narrow contexts of rebellion or invasion, impairing contractual obligations, and altering the Constitution without following the amendment process. These prohibitions serve as essential checks on legislative power, safeguarding individual liberties and maintaining the balance among the three branches of government. Understanding which action Congress cannot perform is not merely an academic exercise; it equips citizens, scholars, and policymakers to recognize when legislative proposals may overstep constitutional limits and to defend the rule of law. By respecting these boundaries, Congress upholds the enduring principles upon which the United States was founded Took long enough..
Adding to this, these explicit textual prohibitions are reinforced by the broader structural principles of separation of powers and federalism. To give you an idea, the principle that Congress cannot vest the judicial power in a non-judicial body (Article III) prevents the legislative branch from adjudicating cases, thereby protecting the independence of the courts. The Constitution does not merely list what Congress cannot do; it establishes a system where certain powers are inherently reserved to other branches or to the states. Similarly, the Tenth Amendment reserves to the states or the people powers not delegated to the federal government, creating a federalist ceiling on congressional authority that cannot be breached by ordinary legislation Worth keeping that in mind. And it works..
These limitations are not static relics of the 18th century. They serve as the foundation for modern jurisprudence and legislative oversight. Here's the thing — when a proposed law raises questions of retroactive punishment, political targeting, or judicial interference, it is these constitutional guardrails that courts and citizens invoke. Also, the enduring strength of the American constitutional project lies in its recognition that limiting power is as crucial as granting it. By defining the boundaries of its own authority, the Constitution ensures that the legislative branch remains a powerful yet constrained actor within a balanced system of government Turns out it matters..
This changes depending on context. Keep that in mind.
So, to summarize, the array of prohibitions—from the specific bans on ex post facto laws and bills of attainder to the structural limits imposed by federalism and the separation of powers—constitutes the Constitution’s essential architecture of restraint. These constraints are not obstacles to effective governance but are, in fact, its very precondition, ensuring that the exercise of power remains legitimate, predictable, and aligned with the fundamental law. Recognizing and upholding these boundaries is therefore the perpetual duty of all who serve within and depend upon the constitutional order.
