Fear is growing in Western capitals that President Trump will yank America out of the North Atlantic Treaty. An untested law, enacted in 2022, requires an act of Congress or approval by the Senate before such a move, but the 1949 treaty includes a loophole to abandon the alliance regardless. 

“Get us out of NATO,” the Utah Republican, Senator Lee, wrote Saturday on X. In a December post, he called the alliance “a great deal — for Europe,” responding to a graph showing that America pays 70.5 percent of the alliance’s total.

Mr. Trump’s “special government employee,” Elon Musk, responded to Mr. Lee’s call for a NATO exit, writing, “I agree.” This came as Mr. Trump was suggesting Europe pick up more of the tab for Ukraine’s fight against Russia.

Most of NATO’s members support Ukraine joining their ranks, but not Mr. Trump. “NATO, you can forget about it,” he told reporters on Wednesday. “I think that’s probably the reason the whole thing started,” meaning Russia’s invasion. 

Mr. Trump has often prodded the other 31 NATO members to carry a greater share of the defense burden. Year after year, many pledged to do so, only to lag behind the treaty’s target to spend two percent of GDP on defense and fail to deploy any meaningful assets. 

America’s North Atlantic allies operate a combined total of zero strategic bombers. In a war with Russia, the world’s largest nation by area, they’d be unable to strike Moscow’s industrial heartland. Britain and France are nuclear powers, just without any ICBMs. 

The Ukrainian leader, President Zelensky, sees NATO’s mutual defense clause in Article V as key to ensuring his country’s security. Mr. Trump knows that, with few exceptions, the tanks, planes, and soldiers storming to Kiev’s rescue would be flying the Stars and Stripes. 

“All for one and one for all” was the creed the 19th-century author Alexandre Dumas gave the heroes of his novel, “Three Musketeers.” Article V is interpreted to express that same esprit. Yet the fine print gives Mr. Trump an option if he decides the other Musketeers aren’t pulling their weight. 

The NATO treaty, as is often said of the Constitution, is not a suicide pact. Article V, I wrote for the Sun in January 2024, “‘states that in the event of a strike on a member, each treaty signatory agrees to take ‘such action as it deems necessary, including’ but not requiring ‘the use of armed force.’” 

NATO allies exercised this flexibility after 9/11, the only time Article V has been invoked. The U.K. provided a large military force in Afghanistan. Other nations sent a few soldiers or just offered moral support. Article V didn’t require a total mobilization for war. 

Should Communist China or North Korea attack Hawaii, the NATO treaty would not be triggered, either. Territories that are not in Europe, North America, or “in the North Atlantic area north of the Tropic of Cancer” are excluded by Article VI. 

This is why, when Argentina invaded the Falkland Islands in 1982, the U.K. was unable to call on NATO. If Mr. Trump’s goal is to update the treaty rather than take his bombers and go home, insisting that all 50 states be covered would be a good place to start. 

Until he gets more favorable terms, Mr. Trump could declare that he won’t risk American lives in the event of an attack on a member state. He could say that, under Article V, the “action” America “deems necessary” stops short of military force — a fear already prompting allies to stop dragging their feet.

The law requiring congressional approval to leave NATO is unlikely to tie Mr. Trump’s hands, either. There’s a good chance it’ll be struck down in court. Article II of the Constitution states that the president, not Congress, is “commander-in-chief of the Army and Navy.”

In a Truth Social post on Monday, Mr. Trump promised that his speech to Congress on Tuesday night “will be big.” Whether that means leaving NATO or not, one thing is certain: Western Europe and Ukraine can’t counter Russia alone, and Mr. Trump is the Musketeer with the biggest gun.