North Korea’s latest rocket launch has sent the global community into another frenzy. While diplomats promise more sanctions against Pyongyang, some of South Korea’s leading voices are losing patience with the international community.

The Chosun Ilbo is South Korea’s most respected newspaper and has deep ties to the country’s elites. So a recent unsigned editorial entitled “South Korea Must Discuss Acquiring Nuclear Arms” should make Washington sit up and take notice. It reflects Seoul’s diminishing trust in its American ally...