In the aftermath of NATO-skeptic President-elect Donald Trump’s election, supporters of the alliance are taking solace in a year-old US law that states he cannot exit without Congress approves.
However, Trump may have a workaround – one that he has already employed.
Sens. Tim Kaine (D-Va.) and Marco Rubio (R-Fla.) introduced legislation in 2023 that would require any presidential decision to depart NATO to be approved by two-thirds of the Senate or authorized by an act of Congress. The measure was passed as part of the fiscal 2024 National Defense Authorization Act, which President Joe Biden signed into law.
Legal experts warn that Trump may try to avoid Congress’s NATO guardrail by asserting presidential authority over foreign affairs, a tactic he has already used to circumvent congressional treaty withdrawal constraints.
The rule is “not airtight,” said Scott Anderson, a Brookings Institution expert and senior editor of Lawfare who has advocated for stricter constraints on a president leaving NATO. What it does, he added, is create a direct constitutional confrontation with Congress if a president attempts to withdraw.
“This is not open and shut, this is about Congress telling you you can’t do this, and if you ignore Congress, you’re going to have to fight us in the courts over it,” Anderson informed the audience.
According to Curtis Bradley, the Allen M. Singer distinguished service professor at the University of Chicago treaty School, if Trump simply announced his withdrawal from the alliance, Congress would not have the legal right to sue him for violating the treaty.
The Supreme Court has traditionally decided that institutional conflicts between the branches are political issues best resolved through political means rather than judicial involvement.
“For the issue to be litigated, there would need to be someone with standing to sue,” Bradley stated in an email. “The only party I can think of who might have standing would be Congress itself, but it is not clear that the Republicans in Congress (who will at least control the Senate) would support such a suit.”
Anderson suggested that lawmakers amend the statute by including language explicitly enabling lawsuit, which would increase Congress’ chances of establishing standing in court.
He further notes that, while Congress has the strongest legal standing to suit over a presidential exit from NATO, service personnel or private persons — such as Americans with property in NATO countries — may have valid grounds, but these are less clear. He also mentioned that if both chambers cannot agree, one of them could file a lawsuit.
Even if the Supreme Court took up the case, it is unclear who would prevail because the constitutional issue is ambiguous. Congress has never filed a direct legal challenge to a presidential withdrawal from a treaty.
“It’s very contested legal terrain, and it’s not 100 percent clear,” Anderson admitted.
That does not imply that a withdrawal, if Trump is able to pursue one, would occur fast. Under the NATO treaty, a member state must file a “notice of denunciation” to tell the other members of its decision. The country’s membership would not officially expire until after a one-year waiting period.
Meanwhile, Trump may harm NATO without openly withdrawing. Democratic legislators have warned that he may decline US backing by removing ambassadors or preventing troops from participating in military exercises. Several lawmakers advocated for new legal measures to protect against these hazards in February, but nothing significant has happened since.
“Following Trump’s threats in his first term, the Congress — recognizing the vital importance of NATO — acted on a bipartisan basis to prevent any future presidents from unilaterally withdrawing,” said Sen. Chris Van Hollen (D-Md.), a member of the Senate Foreign Relations Committee. “While Trump may resort to his old tricks, we’ll continue working to shore up NATO and stand ready to fight back against any attempts to undermine the strength of this alliance.”
When asked for a reply, Trump spokesman Karoline Leavitt stated, “The American people re-elected President Trump because they trust him to lead our country and restore peace through strength around the world.”
It would not be the first time Trump’s staff disregarded legal procedures for treaty withdrawal.
In 2019, during the debate over the Open Skies Treaty, Congress added a provision in the fiscal 2020 National Defense Authorization Act that requires the defense secretary and secretary of state to notify Congress at least 120 days before withdrawing. The 34-nation accord allows countries to conduct reciprocal surveillance flights to monitor military forces and weapons.
Arms control advocates and internationalists in Congress backed the Open Skies Treaty because, with Russia, the United States, the United Kingdom, and France as signatories, it enhanced transparency and confidence. However, the Trump administration and some congressional Republicans said Russia was violating it and that satellite imaging capabilities rendered the flights outdated.
