The World Health Organization (WHO) holds a central position in international health law as the coordinating body for global public health. The legal basis and binding force of its pandemic declarations remain unclear. This article examines the WHO's legal mandate under the International Health Regulations (IHR 2005), with a focus on Article 12 and the procedure for determining a Public Health Emergency of International Concern (PHEIC). While the IHR provide a binding frame for the notification and assessment of global health threats, the subsequent classification as "pandemic" carries no autonomous legal effect. The resulting gap between soft-law guidance and enforceable obligation weakens accountability and exposes the structural tension between state sovereignty and collective responsibility. Future treaty reform — particularly the forthcoming pandemic instrument under Article 19 of the WHO Constitution — should codify clearer triggers, transparency duties, and compliance mechanisms.