President Trump has pledged to avoid the mistakes of his predecessors and stop North Korea from amassing a nuclear arsenal, and on Monday he took another symbolic step by restoring Pyongyang to the State Department’s list of state sponsors of terrorism. The designation has as much moral as practical impact but is still welcome as diplomatic truth in advertising.

“In addition to threatening the world by nuclear devastation, North Korea has repeatedly supported acts of international terrorism, including assassinations on foreign soil,” Mr. Trump said Monday. He could have been referring to the murder of Kim Jong Un’s half-brother with VX nerve agent at an airport in Malaysia in February, but there is no shortage of terror episodes.

Ronald Reagan put North Korea on the list in 1988 after Pyongyang’s agents assassinated four members of South Korea’s cabinet in Burma and bombed KAL Flight 858, killing 115 passengers. U.S. intelligence agencies believe the North was behind the 2014 cyberattack on Sony Pictures after a Sony comedy mocked dictator Kim Jong Un. The North is also believed to have helped Syria build a nuclear-weapons plant that Israel bombed in 2007. And don’t forget the kidnappings of Japanese civilians and assassinations of dissidents abroad.

In an embarrassing moment of his Presidency, George W. Bush removed Pyongyang from the terror list in 2008 as part of then Secretary of State Condoleezza Rice’s forlorn bid to woo the North into nuclear disarmament. Pyongyang pocketed the concession and promised to end its nuclear program even as it continued work in secret. The North has conducted six nuclear tests, fired ballistic missiles over Japan, and will before long be able to reach the continental U.S. with a nuclear-armed missile.

The re-listing highlights the North’s criminal behavior and will further isolate the regime. Secretary of State Rex Tillerson said Monday he hopes the re-listing will “disrupt and dissuade some third parties from undertaking certain activities with North Korea.”