For more than 30 years, the world’s response to North Korea’s nuclear program has combined condemnation with procrastination. Pyongyang’s reckless conduct is deplored. Warnings are issued that its evolution toward weaponization will prove unacceptable. Yet its nuclear program has only accelerated.

The Aug. 5 sanctions resolution passed unanimously by the United Nations Security Council marked a major step forward. Still, an agreed objective remains to be established. But the North Korean success in testing a prototype intercontinental ballistic missile eliminates the scope for further equivocation. If Kim Jong Un maintains a nuclear program against the opposition of…