In this article, we examine how the tension between justice and force informs the efforts of the United Nations (un) to promote the rule of law through its peace operations. We begin by showing how the un’s discourse of ‘securing peace’ has three antagonistic propositions holding it together in a combustible way. The propositions are: first, peace contains the force of war; second, law contains the force of peace; and third, justice contains the force of law. With the antagonistic arrangement of these propositions in mind, we then show how the un has developed two contrasting approaches to promoting the rule of law through its peace operations, which we describe as its ‘aspirational’ and ‘operational’ visions of the rule of law. The aspirational vision combines the need for an effective and accountable security sector with a focus on the substantive requirements of justice, thus aspiring to bring all three propositions together in the rule of law. By contrast, the un’s operational vision prioritizes security, stability and order, thus losing sight of the importance of justice. We demonstrate this divergence between the un’s aspirational and operational visions through a study of the un’s peace operations in Liberia between 1993 and 2014, with a focus on the rule of law promotion activities of the un Mission in Liberia (unmil). We argue that the un’s efforts to promote the rule of law through its peace operations risk establishing the conditions for a state of tyranny if they lose sight of the antagonistic but co-dependent relationship between justice and force. The challenge is to prioritize the requirements of force and justice at the same time. While this will not resolve their antagonistic relationship, it has the virtue of acknowledging their co-dependency as an uncomfortable yet unavoidable condition of a state based on the rule of law.