Local governments and transnational city networks (‘TCNs’) have been increasingly engaging with norm-generation in the traditionally state-centric international law and migration governance. We identified two modes of this engagement: participation in mainstream state-centric processes, and norm-generation within their own networks. Through four examples, his article identifies four functions of this jurisgenerative activity. Theexternal function is bringing local interests and expertise to influence international normative developments. The internal function is regulating local governments' behaviour towards their own citizens, creating and upholding standards. Through a horizontal function, local governments recruit peers and rally around normative documents that offer a compact, crystallised expression of their interests. The integrating function enables local governments to combine fragmented issues of international law in unified, practical toolkits for their own use. All throughout, TCNs challenge state-centric international law and their traditional exclusion from it by demonstrating competence and fluency in international norm-generation relating to migration.