Donald Trump
Donald Trump; drawing by Siegfried Woldhek

It’s a bullish time for executive power. President Donald Trump’s conception of it is so expansive that he has asserted that he can pardon himself. The Supreme Court has reinforced that conception by upholding Trump’s blatantly anti-Muslim executive order restricting immigration. And Judge Brett Kavanaugh’s probable confirmation will produce a decisively right-leaning court likely to be deferential to a Republican president like Trump. Trump’s belief that presidential authority is practically monarchical, his belligerent posturing toward countries such as Iran and North Korea, and his cavalier disregard for legal procedure have made many observers wonder if he will try to start a catastrophic war, and what safeguards exist to constrain him if he does.

In November 1973 Congress passed the War Powers Act, over President Richard Nixon’s veto. The Vietnam War, which had begun as an advisory mission twenty years earlier, had turned disastrous in the hands of the willful and self-deceiving Johnson administration and then the cynical Nixon team. The act was meant to give the legislative branch a measure of control over military engagements by constraining the president’s power to use military force without a congressional declaration of war or other statutory authorization.

Under Article I of the Constitution, only Congress can declare war. But Article II makes the president the commander-in-chief, and in that capacity presidents have initiated and sustained armed conflict without explicit congressional permission. Neither Korea (a “police action,” as Truman put it) nor Vietnam was a declared war, yet over 100,000 Americans and millions of Asians died during them.

The War Powers Act was designed to preclude that kind of escalation. Under it, the president can still deploy US forces before obtaining congressional approval. But the White House has to notify Congress within forty-eight hours any time American troops and other military assets are readied for combat or engaged in hostilities, including in self-defense. After that, the US cannot stay in the conflict for more than sixty days (with an additional thirty days for withdrawal) unless Congress declares war or provides statutory authorization. In effect, then, the president can authorize tactical military action without prior congressional approval in response to an emergent attack or threat, but must obtain such approval for any ensuing military build-up or strategic escalation.

In addition, “where imminent involvement in hostilities is clearly indicated by the circumstances,” the act requires the president to consult Congress before undertaking military action. In this respect, the War Powers Act arguably bars preventive military action—i.e., action to preclude an attack that an adversary is capable of but that is not imminent—without prior authorization from Congress.

Over the past forty-five years, the effective scope of the act has remained more or less the same. Hawks don’t want to press federal courts to clarify how widely it applies for fear of a ruling that would restrict executive power. Doves are afraid the courts will expand it. The courts themselves are wary, too. They tend to regard disputes between the White House and Congress about the applicability of the act as political questions inappropriate for judicial review.

It is impossible to show how many preventive military actions the act has deterred. Congress has occasionally invoked the War Powers Act to limit American military commitments—for example, President Ronald Reagan’s deployment of troops to Lebanon in 1983—but more ambiguous interventions, particularly those with a prominent humanitarian dimension like the ones in Somalia and Kosovo in the 1990s, slipped through the statutory cracks. While many legislators were anguished over Somalia, Senate Majority Leader George J. Mitchell argued that the act exempted humanitarian interventions in which US troops were unlikely to engage in combat, while President George H.W. Bush suggested that the War Powers Act was unconstitutional. President Bill Clinton declined to consult Congress about Kosovo, peremptorily asserting the constitutionality of the US air campaign on the basis of his authority as chief executive and commander-in-chief.

Three days after the attacks of September 11, 2001, a shocked and panicked Congress passed the Authorization for Use of Military Force (AUMF) by a vote of 98–0 in the Senate and 420–1 in the House. (California representative Barbara Lee was the one dissenter.) The law gave the president authority to use all “necessary and appropriate force” against anyone he determined had “planned, authorized, committed or aided” the attacks, or harbored such persons or groups. Three successive administrations have used the AUMF to justify military action in Afghanistan, across the Middle East and North Africa, and in sub-Saharan Africa.

The US invasion and occupation of Iraq was undertaken essentially on the pretext of keeping Saddam Hussein from providing al-Qaeda with weapons of mass destruction that he supposedly (but did not in fact) possess. Congress overwhelmingly approved the invasion (297–133 in the House, 77–23 in the Senate), which was also supported by many journalists and analysts. Energetic and thoughtful arguments for the legality of prevention, based mainly on self-defense, were made before the invasion and in its immediate aftermath.


The current consensus that the wars in Iraq and Afghanistan were strategic disasters has tended to invalidate these positions. But little has been done to limit the executive branch’s broad discretion over matters of national security. The Bush administration acted illegally when it authorized what was euphemistically called the “enhanced interrogation”—that is, torture—of suspected jihadists. Senior Justice Department lawyers, including the head of the Office of Legal Counsel (OLC), which is charged specifically with advising the executive branch on constitutional issues, drafted or approved memos that advanced tendentious legal arguments. The Obama administration was especially fond of drone strikes as a means of counterterrorism enforcement, expanding their use well beyond the level seen during the Bush years, to the consternation of some constitutional and human rights lawyers.

Donald Trump campaigned on a platform of what often looked like America-first isolationism, and in June he suspended joint US–South Korea military exercises to placate North Korean leader Kim Jong-un during their summit in Singapore. But for the most part he has turned out to be a hawkish advocate of American dominance. Trump also clearly has little knowledge or appreciation of established constitutional and other legal constraints on presidential power, and holds legal arguments in greater contempt than either of his two immediate predecessors.

He has exhorted governors to dispatch National Guard units to police the Mexican border in the absence of his coveted wall, which would arguably violate an 1878 statutory provision circumscribing the use of military forces for domestic law-enforcement purposes under the principle of posse comitatus. According to Bob Woodward’s new book, Fear, Trump wanted to assassinate Syrian president Bashar al-Assad in response to his chemical-weapons attack on civilians in April 2017, despite an executive order prohibiting assassinations, which has been in place and honored since 1976. Secretary of Defense James Mattis decided to ignore him.

Trump’s decision to withdraw from the nuclear deal with Iran—a detailed 159-page document with which Iran had been complying—on the nonsensical basis that Iran’s provocations in the Middle East violated its “spirit” was clearly a pretext for weakening Iran’s influence in the region and freeing the United States to attack its nuclear facilities, which could cause a major regional war.

Trump has derided attempts to minimize civilian casualities in drone strikes as “micromanagement,” loosened targeting criteria, delegated increased operational authority to the Pentagon, and decreased the transparency of the decision-making process. In the past year his administration has escalated its operations against al-Shabaab, the al-Qaeda–linked group based in Somalia, and increased the number of US troops deployed there from fifty to five hundred without congressional authorization. (A Green Beret was killed in Somalia in early June.) Likewise no existing congressional authorization arguably covered the missile strikes Trump launched against Syria in April 2017 and April 2018 in response to Bashar al-Assad’s chemical weapons attacks. As the strikes did not target any jihadist elements, they fell outside the scope of the AUMF and were almost certainly illegal. It’s fairly clear that Trump isn’t inclined to share war powers with another branch of government.

So far, Trump’s fickle policy toward North Korea, lurching from dangerous brinkmanship to clueless placation, has not produced any direct confrontations between him and Congress. But it has showed his resistance to any kind of oversight or guidance. The summit’s results asymmetrically favored North Korea: Pyongyang made no major concessions that it hadn’t already made and broken, while Washington implicitly recognized North Korea as a nuclear power and agreed to relieve military and economic pressure on the regime. Precedent as well as post-summit US intelligence reports suggests that any tentative deal will slowly unravel and that the parties will return to the status quo ante. In that case, the Trump administration would likely feel compelled to take an even more aggressive stance against Pyongyang than it had initially, when Trump and Kim traded incendiary threats and Trump seriously considered a limited military strike on North Korea. Trump might initiate a war against North Korea to neutralize its nuclear weapons capability even if no attack against the United States or American interests were forthcoming—in other words, start a preventive war of choice without seeking congressional authorization.

It is important to consider what would constrain Trump if he tried to start an armed conflict with Iran or North Korea without adequately informing, consulting, or obtaining authorization from Congress.

When Nixon started to drink heavily and behave increasingly erratically during the Watergate scandal, Secretary of Defense James Schlesinger, in a singularly “patriotic act of treason,” is believed to have orally instructed the Joint Chiefs of Staff to ignore any orders from the White House initiating military action without his signature.* Secretary of State Henry Kissinger tacitly reinforced this extralegal stratagem by assuming control of US national security policy. This involved raising the alert levels of US military forces, including nuclear ones, during the Yom Kippur War in late October 1973.


Senior members of the Trump administration with military experience—putatively among the few “adults in the room”—may well consider the president as dangerous and incompetent in matters of national security as Nixon was in 1973–1974. But it seems ever less likely that they will rein the president in, either through open resistance or by discreetly dragging their feet. H.R. McMaster, who was a three-star army general on active service when he was national security adviser, is gone, and in any case was unable to find a way to finesse Trump’s impulses. The same goes for White House chief of staff and former marine general John Kelly, whose own hawkish views and ideological sympathies have inclined him to back Trump; Kelly now appears dispirited and on the verge of leaving the administration.

That leaves James Mattis. Schlesinger was a notoriously arrogant civilian technocrat with a fiercely independent streak, whereas Mattis is a former four-star marine general hypersensitive to the president’s—even this president’s—constitutional status as commander-in-chief. And even if he resolved to curtail Trump’s authority, Mattis could find it more difficult to do so than Schlesinger did Nixon’s: in April 2018, when Trump was weighing whether to strike Syria again, Mattis reportedly asked him to obtain congressional authorization first. Trump ignored the request, Mattis fell in line, and American and allied missiles flew. Trump then cut him out of the loop in Singapore when he decided to suspend US–South Korea military exercises.

Richard Nixon
Richard Nixon; drawing by David Levine

Recent additions to Trump’s foreign policy team aren’t likely to restrain him, either. By appointing Mike Pompeo as secretary of state and John Bolton as national security adviser, Trump has surrounded himself with civilians whose ideas mirror his own aggressive foreign policy instincts and his hostility to the rules-based postwar liberal order. Like Trump, both Pompeo and Bolton are hawks who believe in American primacy. Pompeo, who has little experience in executing foreign policy, is an overt Trump loyalist unlikely to seriously challenge the president. In Bolton, Trump has appointed a man with a similarly impetuous and explosive temperament whom neither Mattis nor Kelly favored for the post.

Although Rex Tillerson and McMaster, Pompeo and Bolton’s respective predecessors, were, broadly speaking, moderate realists, they laid the ground for the White House’s bureaucratic autonomy. Tillerson drained the State Department of talented and experienced personnel, disillusioning those who remained; McMaster was unable to establish a process at the National Security Council that would coordinate the flow of information and decision-making among the different intelligence agencies. While Pompeo has scuttled Tillerson’s grand plan to streamline the State Department, it is still reeling from his depredations. Bolton, for his part, has forced personnel changes at the NSC without visibly improving interagency cooperation or its liaison with Congress.

The absence of effective bureaucratic orderliness was painfully evident in Trump’s recent unsettling performances that stunned other senior US government officials, including his lopsided concessions to North Korea at the Singapore summit, his alienation of European allies at the NATO summit, his obsequiousness toward Russian president Vladimir Putin in Helsinki, and his recklessly improvised Iran policy. Trump’s elevation of two officials so clearly unconcerned with interagency consensus, moderation, and coordination reflects his determination to maximally exploit the leeway customarily afforded the president in foreign policy.

Recent revelations in Woodward’s book and in the essay by an anonymous senior administration official published on September 5 in The New York Times have only reinforced perceptions of an unhinged president. These sources cite instances in which conscientious subordinates have restrained Trump’s dangerous impulses. While these anecdotes may reassure some people that the country remains in sound hands in spite of Trump’s gross deficiency as a leader, perhaps more will observe that restraint has arisen on an unsystematic and highly contingent basis, and that the avoidance of disaster may have been largely a matter of luck.

In Congress, there is growing concern that Trump might start an unauthorized war. While he occasionally invokes the separation of powers cynically and without legal credibility in order to insulate himself from criticism—as when he claimed he couldn’t do anything about the separation of families at the border because Congress wouldn’t let him—Trump has no patience for consulting Congress even when it comes to areas, like the declaration of war, over which the Constitution gives the legislative branch significant power.

Obama’s professorial respect for the Constitution and explicit rejection of torture restored some faith in the legal integrity of the OLC. Although the OLC is institutionally resistant to flagrant politicization, since it is part of the Justice Department as opposed to the White House, the torture memos showed that the office was far from immune to it. A biddable OLC, as the one in the George W. Bush administration sometimes was, could surely find enough jurisprudential wiggle room to advise Trump that he could bypass Congress on the way to war.

Accordingly, there has been some bipartisan pressure in Congress for measures that would circumscribe Trump’s war powers. But such measures have not yet gotten wide support. In May 2017, Senators Tim Kaine (a Democrat from Virginia) and Jeff Flake (a Republican from Arizona) introduced legislation that would limit the reach of the AUMF to countries where jihadists or affiliated groups were actively “engaged in hostilities against the United States.” The bill went nowhere, getting mired in committee.

Then, on October 4, 2017, in southwest Niger, fifty heavily armed local jihadists suspected of being affiliated with ISIS ambushed a combined patrol of US soldiers and Nigerien troops. Four US Green Berets and five Nigerien troops were killed during an extended gun battle. Even many informed national security observers, including Republican senators on the Senate Armed Services Committee like Lindsey Graham of South Carolina, claimed they were surprised that the US had troops deployed in Niger at all. (In fact, the approximately eight hundred US soldiers stationed there constitute the second-largest US deployment in a single country on the African continent, after the Combined Joint Task Force–Horn of Africa in Djibouti.) The ambush revived congressional concern about whether the Trump administration—and the executive branch more generally—should be more accountable to Congress and the public for carrying out combat operations as the military effort against terrorism spreads beyond Iraq and Afghanistan.

The circumstances in Niger also raised a complicated legal question about congressional oversight. If, as the Pentagon has claimed, the soldiers were there merely on an advise-and-equip mission or to protect a US base being constructed for intelligence, surveillance, and reconnaissance, their activities fell under the Defense Department’s general authority, under Title 10 of the US Code, over those and other traditional military activities. But if the US forces were involved in counterterrorism reconnaissance or a potential capture effort against a local jihadist network with ambiguous ties to al-Qaeda or ISIS, as some Nigerien sources told the press, the errant operation might have fallen under Title 50 authority. These are often clandestine and conjoined with CIA operations, and they are subject to more stringent (though less transparent) congressional scrutiny than US military activities in the region had generally received.

Also in early October 2017, Senator Bob Corker (Republican of Tennessee), chairman of the Senate Foreign Relations Committee, disturbed by Trump’s “fire and fury” tweet directed at Kim Jong-un in August and subsequent spiraling rhetoric, implied in an interview with The New York Times that Trump was unfit for office and said he could put the nation “on the path to World War III.” In response, Trump derided him as “Liddle Bob Corker” in a tweet. On October 26, Democratic senators introduced a bill, named the “No Unconstitutional Strike Against North Korea Act of 2017,” that would bar the president from launching a preemptive strike—conventional or nuclear—against North Korea without an imminent threat or express congressional consent. The bill was introduced in the House on the same day.

In November the Senate Foreign Relations Committee held hearings on the president’s general authority to wage nuclear war. Expert testimony provided tenuous reassurances: nuclear first use by the United States requires congressional authorization in the absence of an imminent threat, and military officers are entitled to disobey orders they consider illegal. Trump’s tweeted crack in January that his “Nuclear Button” was “much bigger & more powerful” than Kim’s further discomfited the bill’s sponsors, who elicited support for it from their own Twitter followers.

After intense committee debate on the AUMF two days after Trump’s second set of air strikes against Syria in April 2018, Corker introduced a revised version of Kaine and Flake’s bill. While the new legislation would continue to authorize the president to use necessary and appropriate force against al-Qaeda, the Taliban, ISIS, and designated affiliates, it would not authorize the use of force against any nation-state and would require the president to report to Congress all new designated affiliates, the basis for the designation, and each new country in which the United States was using military force within forty-eight hours; such a report would set off the sixty-day limit prescribed by the War Powers Act. Pompeo had broadly supported such a measure as a House member, and six of twenty-one committee members cosponsored the bill.

The bill has been justifiably criticized as containing loopholes that still afford the president too much leeway to expand military conflict. But since its intent was to reassert congressional war-making authority, floor debate would likely fix such problems. Predictably, however, the Trump administration has not endorsed it. Speaker of the House Paul Ryan and Senate Majority Leader Mitch McConnell have consistently thwarted floor votes on war authorization measures. The new AUMF has not been scheduled for such a vote, and the No Unconstitutional Strike bill has gone nowhere in committee in either house.

Besides legislative action, there is another possible legal means of constraining Trump, but not a promising one. Leery senators and representatives could sue him in federal district court in the hope of obtaining a declaratory judgment—a legal resolution of disputed interpretation of law to inform future action—that the War Powers Act requires the president to obtain Congress’s approval before undertaking preventive military action. In Campbell v. Clinton (2000), thirty-one House members challenged the legality of President Clinton’s conduct of the Kosovo war on the grounds that it violated both the war powers clause of Article 1 of the Constitution and the War Powers Act. The district court avoided a substantive ruling, however, by dismissing the case on the grounds that the plaintiffs lacked standing—one of several procedural devices courts use to avoid having to make a decision—and the court of appeals agreed.

Lawyers for the plaintiffs in a case against Trump might observe that Campbell v. Clinton was decided before September 11 and in particular before the 2003 invasion and occupation of Iraq, which de facto normalized preemptive and preventive military action. Even if the legality of preemption—that is, military action to forestall an imminent attack—is reasonably well established as a justifiable form of self-defense, that of prevention—that is, military action to preclude an attack of which the target is merely capable—is not. While Congress did authorize the Iraq intervention, no federal court has ruled on the constitutional and other legal constraints on preventive wars. The present court, their argument would continue, should provide needed clarity on preventive military action that would not be authorized by Congress under the War Powers Act and that could escalate into a major (and possibly nuclear) war. Such a remedy seems unlikely given the federal courts’ traditional deference to the White House on foreign policy. In any case, a ruling adverse to the president would inevitably reach the Supreme Court, which would probably reverse it.

Constitutionally and statutorily, Congress stands unsteadily between Trump and war, and an assertive Congress remains the most reliable mechanism for reining him in. Much of Trump’s base is tolerant of his brinkmanship as long as it seems to work. In view of the tribal devotion that many Republican voters have shown toward Trump and their apparent willingness to grant him imperial power, they might be inclined to defend his executive prerogative to go to war.

At the same time, polls indicate that most Americans, after years of frustration and loss in Iraq and Afghanistan, are wary of more war. It’s easy to forget that Trump ran on a quasi-isolationist platform, as he now appears to be setting the stage for military action against Iran. Divided popular opinion on executive war-making power could induce the Republican congressional majority to draw the line before any situation escalates. But if Congress waits for Trump to move decisively toward preemptive or preventive war with Iran or North Korea, there might not be enough time or bureaucratic friction to stop him.

—September 13, 2018