Opinion | Donald Trumps Threat to the Global World Order

The global legal order rests on a kind of collective act of faith.For it to work, nations must trust that other nations will behave as if its principles matter.

The system is not so unlike the dollar in this respect: It holds value only when — and only because — most of those who use it believe that it does.This is why Donald Trump’s re-election to the American presidency is such a threat to global peace and security.He is — as an elected official and as a person — committed to breaking principles, not maintaining them.

He understands and appreciates the value of the dollar.The global legal order? Not so much.The last time he was president, Mr.

Trump withdrew from critical treaties, launched what critics have deemed unlawful military strikes in Syria and on the Iranian general Qassim Suleimani in Iraq, and set off a damaging trade war with China.This time, his incoming administration appears poised to do far worse.

His choice for national security adviser, Representative Michael Waltz, introduced legislation last year to use military force against drug cartels in Mexico.His pick for defense secretary, Pete Hegseth, has championed service members accused or convicted of war crimes.

His choice for director of national intelligence, Tulsi Gabbard, is an apologist for both the Syrian dictator Bashar al-Assad, who has massacred his own people, and Russia’s president, Vladimir Putin, who started an illegal war on Ukraine and is under an arrest warrant from the International Criminal Court.Together with Mr.Trump’s, their ideas embody the rejection of a system that is grounded in the idealistic — but until now remarkably successful — faith in the willingness of nations to abide by a set of shared principles that guide their behavior.

If they have their way and America’s commitment to supporting this legal order ceases, we may find out how much the global rules — and principled American leadership in support of them — really matter.For 80 years,...