Understanding War Powers and War Crimes
What the Law Says and What It Can Actually Do
There’s a certain confidence that shows up in public conversations about war. You hear it in phrases like “that violates the War Powers Act” or “that’s a war crime,” delivered as if the law behind those statements is clear, settled, and universally enforced.
The problem is that it isn’t.
That doesn’t stop activists, politicians, media, and just about anyone opposed to a military action from using them regardless of what the relevant laws actually say, how they function in practice, and where interpretation enters the picture. Before we decide whether something is illegal or criminal - and certainly before insisting upon it in public - we should at least understand what those words mean.
War Powers Resolution
The starting point for any discussion of presidential war powers is the United States Constitution, and it is here that the ambiguity begins. The Constitution gives Congress the power to declare war, raise and support armies, and fund military operations. At the same time, it designates the President as Commander in Chief of the armed forces. On paper, that looks like a clean division of responsibility: Congress decides whether the nation enters a war, and the President conducts it.
What the Constitution does not do is define what counts as a “war.”
Detractors will argue that this distinction is merely semantic; a way to bypass constitutional limits and not what the founders intended. But the gap has mattered from the very beginning. In 1794, during the Whiskey Rebellion, George Washington personally led federalized militia forces to suppress an armed uprising. There was no declaration of war. The action was framed as law enforcement, not war, even though it involved organized military force.
That pattern has repeated itself, in different forms, throughout American history. Military force is used, but it is described as something other than “war”; a police action, a limited engagement, a targeted operation. The terminology changes. The underlying reality does not.
In the Constitution, Congress has the power to declare war. In practice, presidents have often exercised the power to avoid calling it one.
The War Powers Resolution was Congress’s attempt to address this ambiguity. Passed in the aftermath of Vietnam, it was designed to reassert legislative authority over the use of military force without relying on formal declarations that presidents had increasingly sidestepped.
On paper, the mechanism is straightforward. The President must notify Congress within 48 hours of introducing U.S. forces into hostilities or situations where hostilities are imminent. From there, a 60-day clock begins, with an additional 30 days allowed for withdrawal, unless Congress authorizes the action through a declaration of war or other legislation.
As written, it appears to impose a meaningful constraint. In practice, its effect is far more limited.
Presidents have generally complied with the reporting requirements, but they have done so while explicitly maintaining that the Resolution itself is constitutionally questionable. In other words, they follow the process without conceding that Congress has the authority to impose it in the first place.
Congress, for its part, has limited practical enforcement options. Any binding attempt to compel withdrawal would require legislation subject to presidential veto. Overriding that veto requires a two-thirds majority in both chambers; an outcome that is possible in theory but rare in practice.
The courts have largely declined to intervene, treating disputes over war powers as political questions better resolved by the elected branches. As a result, there is no definitive ruling that fully settles the constitutional boundaries of the Resolution and Congress has little incentive to try to force one. An unfavorable ruling by the SCOTUS would not simply affect a single dispute, it could permanently narrow legislative authority. In that sense, ambiguity preserves power in a way that clarity might not.
Even the triggering mechanism - what counts as “hostilities” - has proven flexible. Presidents have, at times, interpreted the term narrowly enough to argue that certain military actions do not start the clock at all. The result is a law that exists, operates, and is regularly referenced, but rarely forces a decisive outcome. It creates a framework for consultation and political pressure, not a hard mechanism for control.
In practical terms, unless Congress is unusually unified against a president and willing to sustain that unity through a veto override, the Resolution does little to compel action. Most of the time, it is not Congress that meaningfully constrains presidential use of force. A more realistic constraint is public opinion.
Military actions, particularly those that extend over time or produce visible consequences, are ultimately subject to political pressure. Public support can provide a president with latitude. Public opposition can narrow it. Congress, in many cases, responds to that pressure rather than initiating it.
Members of Congress are well aware of these dynamics. Public appeals to the War Powers Resolution often function less as attempts to trigger a decisive legal outcome and more as efforts to shape public perception of the underlying action. In that sense, the Resolution operates less as a legal framework than as a political signal.
This does not mean the law is irrelevant. It formalizes communication and creates a record. But as a tool of direct enforcement, it is limited. As a tool of political influence, it is far more active.
War Crimes
If the War Powers Resolution reflects the limits of domestic law in constraining the decision to use force, the concept of war crimes reflects the limits of international law in constraining how force is used.
Most people, when asked where war crimes law comes from, will point to the Geneva Conventions. That’s part of the answer, but it’s not the whole picture. War crimes are also defined through other agreements and through something less visible but just as important: customary international law.
Customary international law is not written in a single document. It develops over time through the consistent practices of states acting out of a sense of legal obligation. It reflects what nations generally accept as binding rules of conduct in armed conflict, even when those rules are not codified in a single treaty. Within that framework, war crimes are defined by a set of established principles; clear in structure, but heavily dependent on context in their application.
First is the principle of distinction. Combatants are required to distinguish between military targets and civilians. Deliberately targeting civilians is prohibited. In practice, however, not every target falls neatly into one category. Many modern targets are dual-use; facilities that serve both civilian and military functions. A power plant, for example, may provide electricity to homes while also supporting military communications or industrial production. In such cases, the target may be considered legitimate if its destruction is expected to provide a concrete military advantage, even if that advantage is ultimately not realized.
This becomes more complicated in extreme cases, such as when military forces operate from within protected civilian sites. The use of a civilian hospital as a weapons depot, for example, is itself a violation of the laws of war, as it misuses a protected medical facility and may, depending on the circumstances, amount to the use of civilians as shields. However, that unlawful use can alter the legal status of the site, potentially making it a legitimate military target. That does not remove all constraints on attacking it; other principles - such as proportionality and precaution - still apply, but it illustrates how the classification of a target can change based on how it is used.
Second is proportionality. Even when a target is legitimate, an attack is prohibited if it is expected to cause civilian harm that is clearly excessive in relation to the anticipated military advantage. This is not a precise calculation. It requires a judgment made in advance, often with incomplete information, about both the value of the target and the likely collateral damage.
The existence of the proportionality rule reflects that civilian harm is not, by itself, unlawful under the law of armed conflict. What the law prohibits is harm that is excessive in relation to the anticipated military advantage.
The law does not define proportionality with numerical thresholds or fixed formulas. Instead, it relies on reasoned assessment under the circumstances at the time. As a result, different observers can reach different conclusions about the same action. Those aligned with the attacking force may view an anticipated military gain as significant, while those aligned with the affected population may view the resulting harm as excessive. The standard itself is legal, but its application inevitably reflects interpretation.
Third is military necessity. Force must be directed toward achieving a legitimate military objective, not applied for its own sake; a principle that largely reinforces the requirements of distinction and proportionality. The phrase “in the circumstances ruling at the time” in ICRC Customary IHL rule 8, reflects a critical feature of the law: decisions are judged based on the information available when they are made, not on outcomes assessed in hindsight. The standard is not whether the decision turned out to be correct, but whether it was reasonable given what was known at the time.
Finally, intent matters. War crimes involve unlawful actions carried out deliberately or with reckless disregard for legal constraints. A tragic outcome, by itself, is not sufficient. Civilian casualties can occur even in lawful operations. The legal question is not whether harm occurred, but whether the action that caused it violated established rules.
Part of that analysis includes the obligation to take feasible precautions to minimize harm to civilians. This can include providing advance warning when circumstances permit, allowing civilians an opportunity to leave an area before an attack. However, this requirement is not absolute. Warnings must be practicable under the circumstances, and in some situations - such as when surprise is necessary or time is limited - they may not be given. The absence of a warning, by itself, does not determine legality, but it is one of several factors considered in assessing whether an operation complied with the law.
Applying these standards requires judgment. What qualifies as “excessive” harm is not a fixed number. What constitutes a legitimate military target can depend on intelligence that is incomplete or disputed. The line between a tragic mistake and a criminal act can hinge on intent, information, and context that are not always visible from the outside. In other words, the definition of a war crime is legal, but the determination of one often is not.
That does not mean the rules are meaningless. It means that applying them is difficult. The fact that an attack causes fear or disruption does not, on its own, establish criminal intent. Even errors in judgment or flawed intelligence are not necessarily war crimes unless they rise to the level of recklessness or intentional wrongdoing.
Beyond these definitional issues lies a more practical constraint: enforcement.
International law is often described as binding, but in practice it depends on the willingness and ability of states and institutions to enforce it. There is no global authority with guaranteed jurisdiction or compliance. International courts rely on cooperation from states, and political considerations often shape who is investigated, who is prosecuted, and who is not.
In short, international law is fully applicable… right up to the point where no one is willing or able to enforce it.
That reality does not negate the existence of the law, but it does shape its impact. Powerful nations are less likely to be subject to external enforcement. Allies may be shielded by political considerations. Even when legal standards are clear, the mechanisms for applying them are uneven.
Historically, enforcement has often followed outcomes as much as principles. War crimes prosecutions tend to occur when there is both the legal basis and the practical ability to impose accountability; conditions more likely to exist when one side has been defeated or otherwise lacks the power to resist jurisdiction. In that sense, the application of international law is influenced not only by legal standards, but by the balance of power.
In both domestic and international contexts, the pattern is similar. The law exists. The language is often precise. But the ability and willingness to enforce that law determines how much it actually constrains behavior.
The War Powers Resolution outlines a process but offers limited means of compelling compliance. The law of war crimes establishes standards but depends on imperfect systems of interpretation and enforcement. None of this makes them irrelevant. It makes them more complicated than they are often presented.
Statements that an attack is “an obvious war crime” or that a military action “clearly violates the War Powers Resolution” are often presented as straightforward legal conclusions. In reality, they are interpretations shaped by incomplete information, questionable legal judgment, and frequently political motivations. Even when a legal argument is plausible, the ability to enforce it remains a separate - and often decisive - question.
Biography
Scott C. Mallett is a writer specializing in political and cultural commentary. A former college professor, he utilizes his classroom experience to present complex issues in a way that is clear, accessible, and easy to understand. His work has been featured on The Hill and National Review, as well as his Substack, The Gospel According to Scott.