As COVID-19 has spread around the world, many states have suspended their compliance with a core requirement of international refugee law: the duty to refrain from returning refugees to territories where they face a serious risk of persecution (the duty of non-refoulement). These measures have prompted some observers to question whether non-refoulement will survive the pandemic as a nonderogable legal duty. This Article explains why the international community should embrace non-refoulement as a peremptory norm of general international law (jus cogens) that applies even during public emergencies, such as the coronavirus pandemic. Viewed from a global justice perspective, the authority that international law entrusts to states—including the sovereign power to regulate migration across national borders—can be legitimate only if states refrain from refoulement. For the international legal order to claim to possess legitimate authority over exiled outsiders, it must treat non-refoulement as a jus cogens norm. A failure to regard non-refoulement as a peremptory norm would thus strip the international legal system of its claim to legality vis-à-vis asylum seekers, supplanting the rule of international law in this context with mere coercive force. To test this account of the authority of international refugee law, the Article surveys closed-border policies that states have adopted in response to COVID-19 and explains why the associated restrictions on non-refoulement are unjustifiable and incompatible with the rule of law. Even during a genuine national emergency, such as the COVID-19 pandemic, receiving states cannot return refugees to persecution without subverting their own claims to legal authority.