Though recent years have seen a proliferation of critical histories of international law, their normative significance remains under-theorized, especially from the perspective of general readers rather than writers of such histories. How do critical histories of international law acquire their normative significance? And how should one react to them? We distinguish three ways in which critical histories can be normatively significant: (i) by undermining the overt or covert conceptions of history embedded within present practices in support of their authority; (ii) by disappointing the normative expectations that regulate people’s reactions to critical histories; and (iii) by revealing continuities and discontinuities in the functions that our practices serve. By giving us a theoretical grip on the different ways in which history can be normatively significant and call for different reactions, this account helps us think about the overall normative significance of critical histories and how one and the same critical history can pull us in different directions.