Can Congress Prevent Trump From Exiting NATO?

It's not every day that a former (and perhaps future) U.S. president says to NATO members that he'll allow an adversarial nation to "do whatever the hell they want" if those allies don't pay up. Nor is it every day that a presidential candidate threatens to withdraw from the alliance altogether.

With NATO hanging in the balance, Congress has sought to prevent the executive office from being able to take the United States out of the alliance. At the end of 2023, after over five years of consideration, Congress finally passed legislation barring any future U.S. president from unilaterally withdrawing from NATO.  

Notwithstanding this legislation, if a president’s intention to leave NATO is indeed serious, as former Trump National Security Advisor John Bolton believes is the case with Donald Trump, the commander-in-chief would have many perfectly legal ways to limit U.S. participation in the alliance without formal withdrawal. A U.S. exit in any informal or formal way would most likely spell an end to NATO itself. 

Come Inauguration Day, we may face a scenario in which the only nation to have formally benefited from the invocation of NATO’s Article 5 could bring about its untimely demise. Another possible scenario is an unsustainable two-tiered NATO system whereby the United States defends countries that meet their spending requirement while abandoning those that do not.  

There’s plenty of precedent for the executive branch to draw upon if it wants to quit a treaty. The United States has unilaterally exited over one hundred treaties in the past, including such well-known ones as the 1972 Anti-Ballistic Missile Treaty, from which President George W. Bush withdrew in 2002, and the 1992 Open Skies Treaty, from which President Trump withdrew in 2020. 

The North Atlantic Treaty likewise has an exit clause, and it is quite simple. Article 13 of the treaty states that after the treaty has been in force for twenty years—or beginning on April 4, 1969—leaving NATO would require only a simple notification to other member states. No other legal safeguard exists or would be necessary for a member to withdraw. 

Navigating the Legislative and Legal Landscape 

Over five years ago, the Senate set out to create a legal backstop for a premature U.S. exit from NATO. A bipartisan group of senators led by Virginia Democrat Tim Kaine and Colorado Republican Cory Gardner introduced a joint resolution on July 26, 2018 that would require any president to seek the advice and consent of the Senate before withdrawing from NATO. 

The failsafe mechanism was straightforward: Any president would have to get two-thirds of the Senate to agree to a NATO withdrawal, the same as the requirement for the ratification of a new treaty, but in reverse. It was an unprecedented step—one that garnered significant media attention and expert debate at the time. 

But it wasn’t until the current 118^th Congress that lawmakers finally achieved their goal. The NATO-related legislative language passed Congress this past December as part of the Fiscal Year 2024 National Defense Authorization Act, the annual defense policy bill. President Joe Biden’s signing the act into law was a rare example of a commander-in-chief endorsing a provision that restricts the executive branch’s own powers—usually, the White House lawyers would fight such an outcome tooth and nail. 

The legal issues involved in pre-empting an attempted U.S. exit from NATO are complicated. Members of Congress have already tried multiple times—and failed—to prevent the executive branch from unilaterally exiting other major treaties. 

In December 1978, Senator Barry Goldwater and fourteen other senators filed a lawsuit against President Jimmy Carter to challenge his decision to unilaterally end the U.S.-Taiwan Mutual Defense Treaty in order to normalize U.S. relations with the People’s Republic of China. The following year, the Supreme Court—without hearing oral arguments—sent it back to the lower courts for dismissal, with Chief Justice William Rehnquist arguing for the majority that the case was “nonjusticiable.”

In June 2002, then-Congressman Dennis Kucinich and thirty additional members of Congress filed a lawsuit against President Bush to prevent the withdrawal from the Anti-Ballistic Missile Treaty, similarly arguing that the President could not terminate the treaty without congressional consent. The U.S. District Court for the District of Columbia ended up dismissing the lawsuit. 

Legal scholars differ in their interpretation of these cases and whether they set any kind of binding precedent. In 2018, Harold Koh argued that, “The conventional wisdom that the President possesses a general unilateral power to terminate or withdraw from international agreements is mistaken.” In 2019, Curtis Bradley and Jack Goldsmith argued that it was “unclear” whether congressional legislation actually accomplished the goal of preventing a premature NATO withdrawal, though it “substantially increase[s] the likelihood that courts would adjudicate the merits of a presidential treaty termination.” Last month, Scott Anderson argued that Congress did not do enough and now needs to specifically “pre-authorize litigation” in order to more successfully “challenge any presidential effort to exit NATO contrary to this provision.”

From this legal landscape, the only thing that is evident is that if a future president withdraws from NATO, a long and potentially protracted legal battle between the legislative and executive branches would ensue. 

The Next Battle 

The battle to save NATO from a future commander-in-chief wishing to quit the alliance is far from over. Should a future president choose to proceed with a NATO exit, the executive branch would most likely challenge the congressional restriction in court, claiming that it infringes on the commander-in-chief’s powers granted under the Constitution to conduct U.S. foreign policy. 

In any case, the drawn-out legal fight probably wouldn’t matter much in practical terms. The death blow to NATO could come in the form of a simple U.S. announcement and taking some initial steps toward a premature U.S. exit, such as stopping U.S. contributions to NATO headquarters or the United States’ failing to attend key meetings. 

And if a future president were to issue a similar statement to Trump’s asserting that the United States will not come to the defense of any individual member of NATO if attacked, then the alliance’s crucial deterrence capability could be irreversibly gutted—and there is nothing that Congress would be able to do about it. 

The good news is that the alarm bells have been ringing in NATO member capitals. Russia’s partial invasion of Ukraine in 2014, followed by its full-scale invasion in 2022, has seemingly set the alliance members on the right path to meet their commitments. From 2014 to 2023, European allies and Canada have invested an extra $350 billion in defense, an eight-year consecutive streak of increased spending. 

As of this writing, eighteen out of thirty-one members of the alliance are expected to meet their 2 percent GDP defense spending commitments this year. Its incremental progress that must not only be sustained but seriously increase in the years ahead, especially given the gravity of the Russian threat to Europe. As Putin wages his unjust war in Ukraine, the Russian economy has moved to an all-out war footing: This year, a staggering 30 percent of Russia’s budget expenditures will be defense related.

Now is not the time for the United States to step back from NATO, because the consequences for future generations could be disastrous, much as they were following the U.S. retreat from global leadership in the 1930s. It may well be up to the U.S. judicial system to adjudicate this vital decision in the future. 

Igor Khrestin is the Bradford M. Freeman Managing Director for Global Policy at the George W. Bush Institute. From 2010 to 2021, he worked as senior policy advisor for U.S. Senators Mark Kirk (R-IL) and Cory Gardner (R-CO). 

Image: Sailors assigned to the USS Gunston Hall direct a fast assault craft assigned to Sweden’s 2nd Marine Battalion into the ship’s well deck during NATO exercise Steadfast Defender 24, March 2, 2024. (U.S. Navy photo by Mass Communication Specialist 1st Class Danielle Serocki)