The “responsibility to protect” — known in international-relations circles as R2P — is a straightforward, if often misunderstood, notion: Nations must protect their citizens from genocide, war crimes, crimes against humanity and ethnic cleansing, and must take action to help other nations whose governments can’t or won’t protect their peoples. …

Yet there is one person who has studiously avoided invoking R2P: President Obama. When making the case for airstrikes, he has stressed the need to enforce the worldwide ban on the use and production of chemical weapons. “When there’s a breach this brazen of a norm this important, and the international community is paralyzed and frozen and doesn’t act, then that norm begins to unravel,” Obama warned in a Friday news conference at the G-20 summitin St. Petersburg. …

The official U.S. reticence to emphasize the “responsibility to protect” reflects, in part, a bipartisan reluctance to sign on to anything that smacks of the United Nations. Another possible drawback to R2P is the erroneous perception that it requires a military deployment or other steps that Americans may not believe are in the national interest. R2P contemplates a range of preventive moves intended to forestall the need for military force. If properly working, it should be a stimulus for international action, not a straightjacket.