The primary debate leading into the Iraq war, remember, centered around legitimacy. War critics argued that it was illegitimate for the United States to undertake a war without the consent of the United Nations Security Council.

Daalder and Kagan write that the U.N. Security Council cannot be the final arbiter of American interventions, which is a major concession for Daalder. But they also write that the United States needs some legitimacy for its actions, which is a significant concession for Kagan.
enforcing U.N. resolutionsIsaac Chotiner