Musk wants to leave NATO. Thanks to Marco Rubio, that’s a lot harder

• Elon Musk said he agreed that the US should leave NATO.
• Before he became Secretary of State, Marco Rubio made such a move harder.
• Congress passed a law requiring a vote to approve any US withdrawal.

Elon Musk wants the US to leave NATO. Before he joined President Donald Trump's Cabinet, Secretary of State Marco Rubio made such a historic move a lot more difficult.

"I agree," Musk wrote on X on Saturday night when a conservative political commentator suggested the US leave the United Nations and NATO.

Before he joined Trump's cabinet, Rubio co-led a congressional effort to handcuff any potential future president who wanted to leave NATO. Trump's name wasn't always mentioned, but it was clear his then-presidential candidacy worried enough lawmakers from both parties to move to rein him in.

Musk's comments come at a critical moment.

NATO members, led by the United Kingdom and France, are discussing how to continue to support Ukraine in its war against Russia. Talks between Trump and Ukrainian President Volodymyr Zelenskyy blew up last week. Zelenskyy has said he wants security guarantees as a backstop to any potential peace deal with Russia. The White House proposed a rare earth minerals deal but has been reticent to explicitly lay out a defense plan if Russia violated a potential cease-fire.

Trump has repeatedly expressed skepticism over NATO, particularly the possibility that its mutual defense clause, Article 5, could lead the US into war if a nation like Montenegro was attacked. The president has also threatened to leave the alliance if European nations don't spend more on their own defense.

A White House spokesperson did not immediately respond to a request for comment on whether Musk was speaking in his capacity as a senior advisor to the president. Musk is also the de facto leader of the White House DOGE office.

There could be a legal fight on the horizon.

Under the 2023 law championed by Rubio, any NATO withdrawal requires either the approval of 2/3rds of the US Senate or a separate act of Congress. Given that many GOP lawmakers remain staunch NATO backers, it's extremely unlikely Trump could muster such a large majority.

Legal scholars have said that might not be the last word. Trump could simply ignore the law. His White House has suggested that a different congressional restriction related to spending federal funds is unconstitutional.

In such an event, a legal fight could go up to the US Supreme Court. Historically, the judiciary is reticent to get involved in disputes between branches. There are also concerns about whether lawmakers would reach the threshold of standing, the legal ability to bring such a suit in the first place.

Absent a full US withdrawal, there are other ways to undermine NATO.

A recent wargame found that Trump could simply hollow out the alliance by curtailing US support, allowing NATO to whither.

The US holds a powerful perch at both NATO and the United Nations institutions.

It is the largest member of the NATO alliance, and the only country in its 80-year history to invoke its central defense cause, which came after the 9/11 terror attacks. The US is also one of the five permanent members of the powerful UN Security Council, the only UN group that can impose binding resolutions on all 193 member states.