Abstract : In this paper, we examine how categorization is resisted. We analyze the way actors draw on cultural repertoires to resist or adapt to changes that will potentially alter the definition and nature of the markets in which they compete. We approach this question through a qualitative study of the heated debate over the new regulation of over-the-counter (OTC) financial markets in Europe between 2010 and 2011. Our paper enriches the existing literature on the political nature of categorization. Our results show that in response to unwanted change, incumbent firms try to create incommensurability with their own industry's standard cultural repertoire. Most importantly, this incommensurability is not argued in the name of any higher-order sets of values. Our main contribution lies in the article's focus on the way powerful actors resist categorization, highlighting the link between forms of commensuration and the status of the actors who attempt to instrument it.