In late August 2013, after Syrian civilians were horrifically attacked with sarin gas, President Barack Obama declared his intention to conduct limited airstrikes against the Syrian regime of President Bashar al-Assad. A year earlier, President Obama had announced that the use of chemical weapons was "red line" for the United States. Advocates for military action now argued that if the credibility of American threats diminished, dictators would have license to act with impunity. President Obama himself seemed to embrace this justification for action. "The international community’s credibility is on the line," he said in early September. "And America and Congress’s credibility is on the line." For all the talk of credibility, political scientists have offered devastating critiques of credibility arguments in the context of military threats. They have demonstrated not only that the concept is often deployed in incomplete and illogical ways but also that as a historical matter, a country’s "credibility" based on its reputation and past actions has little or no effect on the behavior of opponents in high-stakes international crises. In the crises in the run-up to World War I, in the Berlin crises of the late 1950s and early 1960s, and even in the crises leading to World War II, threats from countries that had previously backed down were not seen as less credible by their opponents. In some cases, the threats were even thought to be more credible. For constitutional lawyers, this research should be particularly troubling because credibility has migrated from foreign policy into the constitutional law of war powers. In a series of opinions, including on Somalia (1992), Haiti (2004), and Libya (2011), the Justice Department’s Office of Legal Counsel (OLC) has argued that the credibility of the United Nations Security Council is a "national interest" that can justify presidential authority to use military force without prior congressional authorization. This Essay argues that the credibility justification for the use of force should be removed from the constitutional law of presidential war powers. Incorporating credibility as one of the "national interests" that justify presidential use of force expands the President’s war powers significantly without a legitimate policy justification.