Finding that existing theories of International Relations have problems explaining why international Small Arms Control programmes succeed or fail, this thesis explores internationally driven micro-disarmament processes from an agent-driven constructivist perspective. Through two contrasting case studies of the UNDP-led micro-disarmament programme in Kosovo and the EU Small Arms programme in Cambodia, the research considers ways in which local agency deal with ‘norm transfer’ by international organizations. First, the thesis theoretically advances constructivist literature on norm diffusion so to apply to international peacebuilding in general, and Small Arms Control specifically. Treating peacebuilding as exercises in norm diffusion enables more subtle analyses of the political processes involved, taking seriously the politics of norms when international actors get involved in post-war societies. Bringing in dynamic processes of norm localization to the study of micro-disarmament enables better conceptions of agents, processes and mechanisms involved in the reconfiguration of power in peacebuilding contexts. Second, based on extensive fieldwork the thesis provides comparative analyses of how local elites constructed national identity narratives in post-war Kosovo and Cambodia parallel to micro-disarmament processes. In the case of Cambodia, national elites successfully built a narrative of the Khmer nation as idle, peaceful and respectful of authority  an identity consistent with an idea of the state as the legitimate authority over the use of force. Due to enabling social and political factors, the EU Small Arms project supported these discourses of a collective, post-war security culture, and could subsequently contribute to eradicate the small arms problem in Cambodia. In Kosovo, conversely, political elites imbued the post-war nationbuilding process with identity narratives consistent with an individualist security culture. These narratives pitted an autonomous, militant and traditional society against the state monopoly on legitimate use of force. The UNDP Small Arms project did not locate its activities in these discourses, and failed to significantly reduce the availability of small arms in society. The empirical findings of this thesis point to a real need for international organizations to allow local conceptions of legitimacy to take centre stage when introducing democratic security models in post-war countries. Consistent with constructivist scholarship, it finds that norms, culture and identity are not secondary considerations, but effectively produce actors’ preferences and interests. International norm proponents must engage local rationalities when seeking to transfer norms – even in matters of ‘hard’ security.