A US exit from NATO under Trump would likely trigger a legal showdown

• President-elect Trump has warned he may try to withdraw the US from NATO.
• Any attempt would counter Congress and venture into uncharted legal waters.
• A legislative expert saw signs that could favor Congress in this largely untested area.

In 2018, President Donald Trump privately warned that he might withdraw the US from NATO. He complained that other alliance members weren't contributing their fair share of defense spending, which left American taxpayers to pick up the tab.

Congress thought otherwise. It added a special provision in the 2020 National Defense Authorization Act, which sets funding for the US military. Section 1250A specifies that the president cannot unilaterally withdraw America from NATO without an act of Congress, or unless two-thirds of the Senate concur.

Should Trump follow through during his second term, which starts Monday, the withdrawal would fall into a legal gray area likely to be settled in court and that may favor Congress. The problem is that while the Constitution specifies that the president has the power to negotiate treaties, it doesn't say whether he has the power to break them.

"Although Congress has to some extent regulated the President's withdrawal from a treaty in the past, Section 1250A is the first statute in which Congress has prohibited unilateral presidential withdrawal from a treaty," according to a report by Karen Sokol, a legislative attorney for the Congressional Research Service, which analyzes issues for Congress.

The Founding Fathers were rightly proud that they created a government of checks and balances, where neither the executive, legislative or judicial branches could monopolize power. But they probably would be less than thrilled with the dispute over NATO, which America was instrumental in forming 75 years ago, when a devastated Europe appeared easy prey for Soviet conquest.

Normally, the executive branch handles most foreign policy and national security matters such as negotiating treaties, though Congress exercises considerable clout through defense budgets, ratifying treaties, and approving arms sales. Powers between the executive and legislative branches are delineated clearly enough that for the most part, the system works.

When the executive and legislature can't agree, the courts are supposed to step in. Yet of all the myriad issues that end up in American courts, foreign policy is the area that judges are most reluctant to touch. In the case of withdrawing from NATO, the courts will search for legal precedents in an area that lacks them.

The White House has long maintained that it can withdraw from treaties absent Congressional opposition, such as when the Carter Administration withdrew from a mutual defense treaty with Taiwan, which Senator Barry Goldwater and other members of Congress then appealed to the courts. "Ultimately, the Supreme Court declined to weigh in on the dispute," Sokol noted. "With a plurality of the Justices concurring in the judgment to dismiss the complaint, concluding that the case presented a political question that was properly addressed by the political branches rather than the judiciary — a determination that is not uncommon in cases involving separation- of-powers disputes in areas of foreign policy."

In 2020, at the end of Trump's first term, the Department of Justice published an opinion that asserted treaty withdrawal is an exclusive presidential power that Congress cannot restrict. And the Supreme Court has ruled that the executive branch has the authority to recognize foreign governments, even though that power is not specified in the Constitution.

Yet past cases suggest that the courts may reject this argument. Sokol points to the 1952 Youngstown Steel case, when the Supreme Court ruled against President Harry S. Truman's attempt to seize steel mills during the Korean War, on the ground that this violated the intent of Congress.

"Under the Youngstown framework, courts assess presidential claims of authority based on what Congress has—or has not—said about the matter," Sokol wrote. By that standard, Congress has expressed its intent that the US remain in NATO by passing Section 1250A.

Sokol also believes that the courts may reject the Trump administration's assertion that the executive branch alone can decide to withdraw from treaties. "A court may find a President's claim of exclusive constitutional power to withdraw from a treaty to be unpersuasive given that the Constitution is silent about treaty withdrawal powers and that Article II makes treaty entry a power shared between the President and the Senate."

Either way, the question of whether Trump has the power to withdraw from NATO means venturing into largely uncharted legal waters. "Ultimately, it is uncertain how a court would rule on the constitutional distribution of treaty withdrawal power based on its analysis of the Constitution's text and structure, relevant Supreme Court precedent, and historical interbranch practice," Sokol concluded.

Trump may not need to formally withdraw from NATO to damage it. For example, a wargame run by British experts last year found that Trump could sabotage the alliance simply by having America do less. This could include minimizing US participation in NATO exercises or restricting American officers serving as NATO commanders. The effects of a US pullback would be global and hard to predict.

Michael Peck is a defense writer whose work has appeared in Forbes, Defense News, Foreign Policy magazine, and other publications. He holds an MA in political science from Rutgers Univ. Follow him on Twitter and LinkedIn.