In response to the 2009 H1N1 influenza pandemic, the governments of Japan and the United States for the first time authorized the emergency use of unapproved drugs. In this article, we comprehensively review the different regulatory approaches of Japan and the United States, countries with advanced regulatory and healthcare systems, to emergency authorization of the use of medical products as a countermeasure to public health emergencies. We outline the legal system, range of targeted products, requirements for the application dossier, legal stance for authorization, product availability, and termination of the Japanese Emergency Approval (EA), and we compare characteristics with those of the US Emergency Use Authorization (EUA). We also review the actual cases of these 2009 emergency authorizations. The Japanese EA importation of novel H1N1 influenza vaccines with adjuvant is presented, with lessons learned, and contrasted with the US EUA of peramivir.