How Congress Can Stop Wars

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The U.S. Constitution doesn’t hand war powers to one person. Instead, it creates what constitutional scholar Edward Corwin called an “invitation to struggle” between the President and Congress over who controls American military action.

The Framers, fresh from fighting a king, deliberately split up the power to make war. They gave most of it to Congress—the branch closest to the people. But they made the President commander in chief once a war starts.

This was the point. The Framers wanted to make sure that sending Americans into battle would require serious debate, not just one person’s decision.

Congress Gets Most of the War Powers

The Power to Declare War

Article I, Section 8 gives Congress the power “To declare War.” This isn’t just ceremonial language. It makes Congress the only branch that can officially move the country from peace to war.

Congress has formally declared war only 11 times in five different conflicts. The last time was World War II. But the Supreme Court has said this power also lets Congress authorize military operations that don’t rise to full-scale war.

The Power of the Purse

Here’s Congress’s most powerful weapon: control over spending. Article I, Section 9 is crystal clear: “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.”

This means no military operation can survive without money from Congress. It doesn’t matter how badly a President wants a war—without congressional funding, it can’t happen.

Powers Over the Military

Congress also gets to “raise and support Armies,” “provide and maintain a Navy,” and “make Rules for the Government and Regulation of the land and naval Forces.”

The army funding comes with a two-year limit. This was meant to prevent a large permanent military that could threaten civilian control of government.

These powers let Congress control the size, structure, and legal framework of the armed forces. Congress writes military law through statutes like the Uniform Code of Military Justice.

Other War-Related Powers

The Constitution gives Congress other military authorities:

• Issue “Letters of Marque and Reprisal” (now obsolete—this let private citizens attack enemy ships)
• Make rules about capturing enemy property
• Call up state militias to enforce laws, stop rebellions, or repel invasions

The President as Commander in Chief

Article II makes the President “Commander in Chief of the Army and Navy of the United States.” This gives the President the main role in how wars are fought once Congress authorizes them.

Most experts agree this also lets the President repel sudden attacks without asking Congress first.

But how far can a President go without congressional approval? That’s one of the biggest unresolved questions in American law.

Presidential Power Creep

Since World War II, Presidents have claimed broader and broader authority. They argue the Commander in Chief role lets them deploy forces whenever they think it protects U.S. “national interests.”

This has created ongoing tension with Congress. The Constitution sets up war-making as a shared process, not a solo act. The Framers wanted to force cooperation and debate before committing to war’s grave consequences.

But when Congress doesn’t push back hard against presidential overreach, it allows executive war powers to grow. Presidents start new military operations and claim they had the authority all along. Future Presidents then build on those precedents.

Tools Congress Uses to Limit Military Operations

The War Powers Resolution: Congress Fights Back

Born from Vietnam

By the early 1970s, Congress was fed up. The Vietnam War had expanded across Southeast Asia without a formal declaration of war. Revelations about the “imperial presidency” made things worse.

In 1973, Congress passed the War Powers Resolution over President Nixon’s veto. The goal was to make sure both Congress and the President would have a say in military action.

How the Resolution Works

The War Powers Resolution tries to reassert congressional authority through specific rules:

Consultation: The President must consult with Congress “in every possible instance” before introducing forces into combat. In practice, Presidents often interpret this as simply informing congressional leaders after they’ve already decided.

Reporting: The President must submit a written report within 48 hours of introducing armed forces into hostilities, foreign territory while equipped for combat, or in numbers that “substantially enlarge” existing forces.

The 60-Day Clock: This is the heart of the resolution. Once a “hostilities” report is submitted (or should have been), the President must end the use of armed forces within 60 days. This can be extended by 30 days if needed for safe withdrawal.

The clock stops only if Congress declares war, passes a specific authorization, or can’t meet due to an attack on the United States.

Congressional Action: The resolution sets up fast-track procedures so Congress can vote on authorization or withdrawal without getting stuck in committee.

Why It Doesn’t Work Well

The War Powers Resolution has major problems:

Presidential Defiance: Every President since Nixon has said the resolution is unconstitutional. They submit reports “consistent with” rather than “pursuant to” the resolution—a legal way of saying they’re cooperating voluntarily, not because they have to.

The “Legislative Veto” Problem: The original resolution let Congress force troop withdrawal through a concurrent resolution that didn’t need the President’s signature. But the Supreme Court’s 1983 decision in INS v. Chadha struck down similar “legislative veto” provisions in other laws, weakening this congressional tool.

The “Hostilities” Loophole: The 60-day clock only starts with “hostilities.” Presidents have exploited this by defining their military actions very narrowly. In 2011, the Obama administration argued that the Libya air campaign didn’t count as “hostilities” because U.S. forces played a supporting role with no ground troops and limited casualty risk.

Limited Impact: Critics say the resolution has largely failed to rein in presidential war-making. Some argue it’s been counterproductive, creating a perception that Presidents get a “free” 60-to-90-day window for unilateral military action.

The Resolution’s Unintended Consequences

The War Powers Resolution has fundamentally shifted how we argue about war powers. Instead of debating the President’s broad constitutional authority to intervene militarily, we now fight over whether a specific operation meets the definition of “hostilities.”

This shift actually helps the White House. By controlling how they define their own actions, Presidents can often control the legal consequences and sidestep the resolution’s limits.

The resolution’s power also gets undermined by broad, open-ended military authorizations. The 60-day clock only applies when there’s no “specific statutory authorization” from Congress. Laws like the 2001 Authorization for Use of Military Force serve as permanent escape hatches for the executive branch.

The Ultimate Weapon: The Power of the Purse

The Constitutional Foundation

While debates over war powers often focus on declarations and authorizations, Congress has a more fundamental authority: the “power of the purse.”

The Constitution’s Appropriations Clause is stark: “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.” This isn’t just an accounting rule—it’s a cornerstone of separated powers.

In theory, Congress can stop any war at any time simply by refusing to pay for it.

Vietnam: When Congress Cut the Cord

The most dramatic use of the power of the purse happened during Vietnam. By the early 1970s, public and congressional opposition had reached a fever pitch.

After formally repealing the Gulf of Tonkin Resolution in 1971, Congress began using its spending power to force U.S. withdrawal.

Between 1973 and 1974, lawmakers attached amendments to must-pass bills. The most definitive was a provision in the Foreign Assistance Act of 1974, which banned using any appropriated funds for U.S. military activities “in or over or from off the shores of North Vietnam, South Vietnam, Laos or Cambodia.”

With its funding cut off, the executive branch had no choice but to end all U.S. combat operations in the region.

Modern Constraints

While the power of the purse is absolute in theory, it faces practical limits:

The Impoundment Control Act: After Nixon tried to defund programs by refusing to spend appropriated money, Congress passed the Impoundment Control Act of 1974. This prevents Presidents from using administrative delays as a backdoor line-item veto.

Political Reality: Legislators hate taking actions that look like “cutting off funding for the troops.” This political dynamic makes the power of the purse a “nuclear option”—a tool typically used only late in unpopular, long-term conflicts.

This means the power of the purse works better as a reactive tool for ending unpopular wars than as a proactive tool for preventing them. At the start of military operations, when patriotic sentiment runs high and costs aren’t yet apparent, it’s extremely difficult for Congress to deny funding.

Executive Workarounds

The executive branch has historically sought ways around Congress’s fiscal control. The Iran-Contra affair is a classic example—faced with a congressional ban on funding Nicaraguan Contras, Reagan administration officials sought “unofficial funds” through illegal arms sales to Iran.

Modern executive agencies have limited authority to “reprogram” funds between accounts, flexibility that can be exploited to fund activities Congress hasn’t explicitly approved.

For Congress to effectively use its power of the purse, it must be extraordinarily precise in its legislative language and conduct rigorous oversight to ensure the executive branch isn’t subverting its will through creative accounting.

The Blank Check Problem: Modern Military Authorizations

From Declarations to Authorizations

Since World War II, Congress hasn’t issued a formal declaration of war. Instead, when it chooses to approve military action, it passes joint resolutions called Authorizations for the Use of Military Force (AUMFs).

These provide the President with the “specific statutory authorization” required by the War Powers Resolution to conduct hostilities beyond 60 days. Unlike war declarations, which trigger broad domestic emergency powers, AUMFs are meant to be more limited—authorizing force against specific nations, organizations, or for particular purposes.

But the language can be dangerously imprecise, with profound consequences for the balance of war powers.

The 2001 AUMF: The “Endless War” Authorization

The 2001 AUMF is the most consequential military authorization of the 21st century. Passed with only one dissenting vote—from Representative Barbara Lee, who warned it was a “blank check”—in the aftermath of September 11th.

The resolution authorized the President to use “all necessary and appropriate force” against nations, organizations, or persons he determines “planned, authorized, committed, or aided” the attacks or harbored those responsible.

At the time, the targets were understood to be al-Qaeda and the Taliban regime in Afghanistan. But the AUMF was drafted without a sunset clause, geographic boundaries, or a specific list of enemy groups.

This vague language has allowed three successive administrations—Bush, Obama, and Trump—to dramatically expand its scope. It’s been interpreted as sweeping global authority for a “war on terror,” used to justify at least 41 military operations in 19 countries.

It’s been cited as legal basis for action against groups that didn’t even exist on 9/11, such as ISIS, based on the theory that they’re “associated forces” of al-Qaeda.

There’s now broad, bipartisan consensus that the 2001 AUMF is dangerously outdated and stretched far beyond its original intent. This has led to numerous efforts to repeal and replace it with more specific, time-limited authorizations. So far, these efforts have failed to become law.

The 2002 Iraq AUMF

The 2002 Iraq authorization was more narrowly tailored. It authorized the President to use armed forces as “necessary and appropriate” to “defend the national security of the United States against the continuing threat posed by Iraq” and to “enforce all relevant United Nations Security Council resolutions regarding Iraq.”

While its original purpose—addressing Saddam Hussein’s regime—is now obsolete, the 2002 AUMF remains on the books. It was cited by the Trump administration as part of the legal justification for the 2020 airstrike that killed Iranian General Qasem Soleimani in Iraq.

Like the 2001 AUMF, it’s been the subject of bipartisan repeal efforts that have gained traction but haven’t become law.

The Delegation Problem

Vaguely worded AUMFs have become a primary vehicle for eroding congressional war powers. By granting the President broad discretion to determine the enemy and battlefield, these statutes effectively delegate Congress’s constitutional authority to the executive branch, sometimes for decades.

The phrase in the 2001 AUMF authorizing force against those the President determines were responsible for 9/11 is a key example. It created a “blank check” that allowed the executive branch to unilaterally expand the list of targets and geographic scope without ever returning to Congress for a new vote.

A legislative act intended to authorize a specific, limited response to a national tragedy became the legal foundation for a multi-generational global conflict—a direct result of Congress’s failure to include clear limits and a sunset clause.

The political difficulty of repealing an AUMF, even one widely acknowledged as obsolete, reveals powerful institutional inertia. Many legislators fear that voting to repeal could expose them to political attacks for being “soft on terror” or “tying the President’s hands” should a future attack occur.

This dynamic creates political risk that often outweighs the institutional desire to reassert constitutional authority, allowing outdated war authorizations to persist indefinitely.

Congressional Oversight: The Power of Scrutiny

“Continuous Watchfulness”

Beyond its explicit legislative powers, Congress wields significant influence through oversight—the continuous review and supervision of the executive branch. This function is implied in the Constitution’s grant of legislative power and is essential for ensuring laws are implemented as Congress intended.

Oversight is primarily carried out by the standing committee system.

For military matters, the most important bodies are the House and Senate Armed Services Committees, the Foreign Relations/Affairs Committees, and the defense subcommittees of the Appropriations Committees.

The Armed Services Committees handle general defense policy, ongoing military operations, and the annual National Defense Authorization Act (NDAA)—a massive policy bill that sets the budget and priorities for the Department of Defense.

In the Hearing Room

The most visible form of oversight is the committee hearing. Committees regularly call senior civilian and military officials—from the Secretary of Defense to combatant commanders—to testify in public and closed sessions.

These hearings cover budget requests, the strategic “posture” of military commands around the globe, major weapons systems development, military personnel welfare, and the conduct of ongoing operations.

Congressional committees have held numerous hearings on the conflict in Yemen, where members grilled administration officials about the legality of U.S. support for the Saudi-led coalition, the humanitarian consequences, and whether U.S. aid was being diverted to Houthi forces.

These hearings serve multiple purposes: they gather information, force the executive branch to justify policies on the public record, attract media attention to issues, and build a factual foundation for potential legislative action.

The Church Committee Legacy

While routine hearings are the bread and butter of oversight, Congress can launch sweeping investigations. The quintessential example is the 1975 Senate Select Committee to Study Governmental Operations with Respect to Intelligence Activities, known as the “Church Committee” after its chairman, Senator Frank Church of Idaho.

Spurred by explosive news reports about CIA assassination plots and illegal domestic spying by the FBI and NSA, the Church Committee conducted a monumental 16-month investigation.

Its final report documented decades of shocking abuses, including:

• Operation MKULTRA, where the CIA conducted mind-control experiments on unwitting citizens
• COINTELPRO, an FBI program to disrupt civil rights and anti-war groups
• Project SHAMROCK, an NSA program to illegally collect Americans’ telegrams

The committee concluded that “intelligence agencies have undermined the constitutional rights of citizens” because constitutional checks and balances hadn’t been effectively applied.

The Church Committee’s work led to landmark reforms that reshaped American intelligence and oversight:

• Creation of permanent intelligence oversight committees in both chambers
• Passage of the Foreign Intelligence Surveillance Act (FISA) of 1978 to regulate domestic surveillance
• A formal presidential executive order banning political assassinations

The committee proved the vital need for Congress to have access to classified information and exercise what Senator Church called “vigilant legislative oversight” over the nation’s most secret agencies.

The Senate’s Unique Powers

Advice and Consent

The Senate has a unique check on executive power under Article II, Section 2: the power of “Advice and Consent.” This requires the President to secure Senate approval for two critical foreign policy functions:

Treaties: The President can make treaties, but they only become law if ratified by a two-thirds Senate vote. This high threshold gives a significant minority of senators the ability to block major international agreements, including mutual defense pacts, arms control treaties, or status of forces agreements governing U.S. troops abroad.

Confirmations: All cabinet secretaries, ambassadors, federal judges, and high-ranking military officers must be confirmed by a Senate majority. This confirmation process provides a powerful forum for relevant committees to scrutinize a nominee’s qualifications, character, and policy views.

During the 2025 confirmation hearings for President-elect Trump’s Defense Secretary nominee Pete Hegseth, senators aggressively questioned him about controversial statements on women in combat and “wokeness” in the military. This public grilling forced the nominee to moderate his positions and make policy commitments as a condition of potential confirmation.

The confirmation process is thus a crucial vehicle for transparency, accountability, and direct senatorial influence on military leadership and direction.

Congressional Power in Action: Modern Case Studies

Libya (2011): Sidestepping the War Powers Resolution

The 2011 NATO-led military intervention in Libya showed both how the executive branch circumvents the War Powers Resolution and how Congress struggles to respond effectively.

The Obama administration justified initiating air strikes to prevent a humanitarian massacre by Muammar Gaddafi’s forces by citing the President’s Article II authority and a U.N. Security Council resolution authorizing a no-fly zone.

Crucially, the administration argued that the U.S. military’s role—limited to air and naval support, with no ground troops and low casualty risk—didn’t constitute “hostilities” under the War Powers Resolution. This interpretation let the White House evade the 60-day clock that would have forced termination without congressional approval.

The move prompted fierce backlash from both parties. The House passed a non-binding resolution (H.Res. 292) rebuking the President for failing to provide a “compelling rationale” for the intervention.

Lawmakers introduced measures requiring troop withdrawal and prohibiting funding for the operation, but none passed both chambers. The Libya case became a textbook example of how a President can use narrow legal interpretations to sidestep the War Powers Resolution and how a divided Congress can struggle to mount effective response without using its most powerful tool: the power of the purse.

Syria (2013): When Congress Says No

Two years after Libya, the war powers dynamic shifted dramatically. In August 2013, following a horrific chemical weapons attack by Bashar al-Assad’s regime, President Obama announced his intention to conduct punitive military strikes against Syria.

In a surprise move acknowledging the shifting political landscape, the President announced he would first seek congressional authorization.

What followed was a powerful demonstration of Congress’s ability to halt a war before it begins. The administration faced a groundswell of opposition from a war-weary public and deeply skeptical Congress. Members from both the anti-interventionist right and progressive left voiced strong objections to another Middle East military entanglement.

Internal whip counts in the House and Senate made it clear that the authorization bill (S.J.Res. 21) was heading for decisive and politically embarrassing defeat, particularly in the House.

Faced with near certainty of public legislative rebuke, the Obama administration quickly pivoted and embraced a diplomatic solution: a deal negotiated with Russia for Syria to surrender its chemical weapons stockpile for destruction. No vote was ever taken.

The Syria case powerfully demonstrates Congress’s “pocket veto” over military action. It showed that the credible threat of legislative opposition can be as powerful a constraint on the President as an actual vote, forcing the executive to back down and seek alternative solutions.

Yemen: A Sustained Campaign

The multi-year effort by a bipartisan coalition to end U.S. support for the Saudi-led war in Yemen showcases how sustained, multi-pronged campaigns can successfully limit U.S. involvement in foreign conflicts.

For years, the U.S. military provided critical logistical and intelligence support to the coalition, including in-flight refueling of Saudi and Emirati warplanes conducting bombing raids in Yemen.

As the war created the world’s worst humanitarian crisis and caused thousands of civilian casualties, a diverse congressional coalition grew determined to end U.S. complicity. These members deployed nearly every tool in the congressional arsenal:

Oversight and Public Pressure: Committees held hearings highlighting the war’s devastating humanitarian impact and questioning the legality of U.S. involvement.

Targeted Legislation: Senators Todd Young (R-IN) and Jeanne Shaheen (D-NH) introduced bipartisan legislation that would have prohibited U.S. refueling of Saudi coalition aircraft unless the administration could repeatedly certify that the coalition was taking concrete steps to avoid harming civilians.

War Powers Resolutions: In 2019, for the first time in history, both chambers passed a joint resolution invoking the War Powers Resolution to direct the President to remove U.S. forces from hostilities in Yemen. President Trump vetoed the measure, but the votes demonstrated clear congressional majority against the administration’s policy.

Power of the Purse: Lawmakers successfully included provisions in the annual National Defense Authorization Act explicitly banning the use of funds for in-flight refueling of coalition aircraft.

This sustained, multi-front pressure campaign eventually yielded results. In 2018, the Trump administration announced it would end U.S. refueling operations for the coalition. The Biden administration later announced an end to U.S. support for “offensive operations” in Yemen and a review of arms sales.

The Yemen case demonstrates that while no single tool may be sufficient, a coordinated and persistent congressional campaign using oversight, targeted legislation, and the power of the purse can successfully alter U.S. military policy.

The Limits of Congressional Power

These modern cases reveal that successful congressional efforts to limit military operations rarely hinge on a single, dramatic vote. The Yemen example shows Congress is most effective when it orchestrates coordinated campaigns applying pressure from multiple points simultaneously.

Public hearings raise awareness and build a record. Targeted bills impose specific conditions. War Powers resolutions force floor debates and symbolic votes. Riders on appropriations bills cut off specific, tangible forms of support.

No single action was the silver bullet, but their cumulative effect created undeniable political momentum that forced change in executive policy.

The Syria case reveals a more subtle but equally important aspect of congressional power. The anticipation of congressional opposition can be as powerful a deterrent as an actual vote.

President Obama asserted he had constitutional authority to strike Syria unilaterally, yet he chose not to. The reason was political: launching significant military operation in the face of clear, strong, bipartisan congressional opposition would have severely damaged his political capital and undermined his legitimacy both at home and abroad.

The whip counts showed he would lose a vote, and the threat of that public legislative repudiation was enough to compel him to find another path. This demonstrates that Congress’s power isn’t just in what it formally does, but in what the President calculates it might do.

This “soft power” of political deterrence, though difficult to measure, remains one of the most crucial checks on presidential war-making in the 21st century.

The effectiveness of congressional oversight depends heavily on political will and often bipartisanship. The Church Committee’s historic success was rooted in its bipartisan approach, which gave its findings immense credibility.

In today’s highly polarized environment, oversight can break down along party lines. During unified government, where the same party controls the White House and Congress, oversight hearings may become platforms for supporting administration policies rather than rigorously scrutinizing them.

During divided government, oversight can be weaponized for purely political attacks, potentially undermining its legitimacy and effectiveness. The constitutional power of oversight is therefore always mediated by the political reality of the moment.

Its potential is immense, but its actual use fluctuates dramatically with the partisan landscape. Congress has the tools to limit military operations and check presidential war-making. Whether it uses them effectively depends on the political courage and institutional will of the moment.

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