How and when do intergovernmental organisations (IGOs) promote incorporation of international norms in domestic politics? In this article, I assess the impact of the International Labour Organization (ILO) on national labour regulations. I advance a new argument regarding how and when labour regulations are shaped by the ILO. More specifically, I argue that the ILO can shape labour regulations during the preparatory process of international labour standards. I theorize that the preparatory period of international labour conventions constitutes a propitious condition for mechanisms of elite socialisation, learning and domestic mobilisation. To test our argument, we focus on national dismissal regulations covering the period 1970-2013. The findings provide evidence in line with my argument that states improve their regulations during the adoption process. However, I find no evidence that states improve their regulations after formal adoption. The results have substantive implications for our understanding of IGOs and labor standards in particular.