Sanctions, particularly economic sanctions, have long been a tool of U.S. foreign policy, and few presidents have leaned on them as much as Barack Obama or been as successful at rallying others to do the same. To thwart Iran's nuclear ambitions, the U.S. has cajoled and bullied much of the world to slash imports of Iranian oil and freeze out Iranian banks. Most of the world has similarly choked off trade with North Korea. And for almost two years after the outbreak of Syria's civil war, the U.S., Europe, and the Arab League hoped that asset freezes, banking and visa sanctions, and a Western ban on Syrian oil purchases would pressure Bashar al-Assad to step down or persuade his cronies to oust him.
In a world bristling with bad actors, and especially at a time when the country is wary of another war, sanctions have an obvious appeal—and limited impact. Sanctions have failed to dissuade Iran from continuing to enrich uranium. They haven't dislodged North Korea's repressive and erratic leaders or forced a rollback of their nuclear and missile programs. For all the international pressure on Syria's Assad, the regime is getting more ruthless, not less, and the policy debate in Washington has moved on to how much military support to provide the rebels.