In 2023, Senators Tim Kaine and Marco Rubio passed a law making it harder for a U.S. president to pull out of NATO. The law says any president who wants to leave NATO needs approval from Congress, either through a two-thirds Senate vote or a special act of Congress. This law was designed to stop President Trump from making any sudden moves to pull the U.S. out of NATO after he spent years criticizing the alliance.

But here's the catch: Legal experts believe Trump might still find a way a...