• Trump administration said in 2020 that he could leave treaties
• Congress passed law in 2023 barring unilateral NATO withdrawal
• No NATO member has ever withdrawn from the 77-year-old alliance
• As senator, Rubio helped lead effort to prevent unilateral withdrawal

WHAT DOES U.S. LAW SAY? In 2023, Congress passed, and then-President Joe Biden, a ​Democrat, signed into law, legislation barring any U.S. president from suspending, terminating, denouncing or withdrawing the United States from the treaty that established NATO unless the withdrawal is backed by a two-thirds majority in the 100-member Senate.

TL;DR; Per 2023 Congressional Law, not without a 2/3 US Congressional majority (and with a one year notice to NATO). But, experts said this lack of commitment, rather than any law, was the key point.