Congress approves bill barring presidents from unilaterally exiting NATO

Congress this week approved a measure aimed at preventing any U.S. president from unilaterally withdrawing the United States from NATO without congressional approval. Passage came amid long-standing concerns that Donald Trump may try to exit the alliance if he returns to office.

The provision was included in the National Defense Authorization Act, an annual bill detailing defense policy, which was passed by the House on Thursday and is awaiting the signature of President Biden.

Under the measure, advocated by Sens. Tim Kaine (D-Va.) and Marco Rubio (R-Fla.), the president would be prohibited from withdrawing from NATO without the approval of two-thirds of the Senate or separate legislation passed by Congress.

Kaine and Rubio had tried to advance similar measures since 2021. Passage of the defense policy bill this week marked the first time the House had embraced the tactic.

The Republican-led House Armed Services Committee did not respond to questions about why the chamber accepted the provision. The office of Speaker Mike Johnson (R-La.) declined to comment.

The bipartisan attempt to add checks and balances highlights the lengths Congress is willing to go to protect the U.S.-NATO relationship amid ongoing Russian aggression and following years of criticism of the military alliance during Trump’s presidential tenure.

President Biden has sought to reassert the leadership role of the United States in global diplomacy, helping galvanize NATO member countries in support of Ukraine following Russia’s invasion and encouraging efforts to expand the alliance to include Finland and Sweden.

During his presidency, Trump frequently lambasted the alliance, accusing its members of being “delinquents” and questioning the wisdom of NATO’s collective defense clause.

Article 5 of the North Atlantic Treaty, which formed the legal basis for NATO, states that an armed attack on one member of the alliance will be viewed as an attack on all of them, and that they will defend one other.

In 2018, Trump publicly mused about why the United States might come to the aid of NATO member Monte­negro, saying that sending troops from the alliance to defend an “aggressive” ally could result in World War III.

Former Trump aides, including former national security adviser John Bolton, have said they feared at times that Trump could pull the United States out of the alliance. But Trump and his allies argue that his tough approach to NATO pushed member states to boost their defense spending obligations and strengthened the alliance.

Kaine, in a statement, said that the provision in the defense policy bill affirmed “U.S. support for this crucial alliance” and sent “a strong message to authoritarians around the world that the free world remains united.”

Rubio said in a statement: “The Senate should maintain oversight on whether or not our nation withdraws from NATO. We must ensure we are protecting our national interests and protecting the security of our democratic allies.”

While the defense policy bill is set to be signed into law by Biden, it’s unclear how exactly a scenario might play out in which the president and Congress are at odds over NATO membership.

Michael E. O’Hanlon, a senior fellow at the Brookings Institution, pointed out that there is precedent for presidents withdrawing unilaterally from treaties without consulting Congress. A chief executive conceivably could push back on efforts to restrict that — particularly if the treaty addresses the United States’ defense posture abroad.

A “future president might challenge such an effort and invoke the president’s authorities as commander in chief under Article 2 of the Constitution,” O’Hanlon said in an email. “It would, I think, be uncharted territory if this issue were forced to a confrontation.”

A Kaine aide said that while the Constitution is clear about the process to enter a treaty — including ratification by the Senate — it is silent on withdrawal. The provision offered by Kaine and Rubio was an attempt to offer specific guidance about the process, said the aide, who was not authorized to speak publicly on the legislation and spoke on the condition of anonymity.

If a president violates the law, Congress can seek recourse in the courts, the aide said.