Japan’s new security legislation, enacted on 30 September 2015 and came into force on 29 March 2016, has expanded the scope in which the Japanese Self-Defence Forces (sdf) personnel can use weapons while engaging in a peacekeeping mission. Among other changes, it authorises the sdf to use weapons in order to protect civilians (civilian protection mandate) or to come to the aid of geographically distant units (“come-to-the-aid” mandate). While this policy itself deserves approbation, its implementation by the sdf in peacekeeping operations under the new security legislation requires careful consideration. This article examines the legal quagmire they will encounter due to the recent jurisprudential development and associated debate regarding the regulation of the use of force in peacekeeping under international law and the circumstances where legal obligations may arise to use force in order to protect civilians. It concludes by suggesting the need for Japan to form its own legal position in relation to each of the debatable legal issues and to develop national rules of engagement for each peacekeeping operation they participate in with a view to effectively communicating its legal position in operational terms to its forces.