This paper asks what regulation actually means in practice in the post-economic reform context of India, taking the case of biosafety regulation and Bt cotton as a case. The last few years have been a test case for such regulations, culminating in the formal approval of Bt cotton for commercial production in 2002. The paper explores various dimensions of regulation – narrow and broad, “front end” and “back end”, technical and political. With the opening up of the economy and the encouragement of external investment in areas like biotechnology, biosafety regulation is one area retained by the central state. But how effective is this, given the role of powerful commercial players and the highly diverse set of practices found at more local, state levels? By examining the Bt cotton story in India – and in Karnataka state in particular – the paper demonstrates how – in practice – regulations emerge through a political process of negotiation between a wide range of actors in multiple sites. The result is usually an uneven, and often diverse, compromise, based on a combination of technical, social, political and, sometimes, moral considerations. It is the process of co-construction of policy, operating in a hybrid world between science, business and policy which is key for our understanding of regulation in practice. A particular focus of this paper is the interaction between national and state level processes in the Indian federal system, and an examination of how regulatory debates – formally located at the national level within national ministries and departments, firmly within the Delhi policy circuit – influence and, in turn, are influenced by what happens at a state level. Across these sites – all under the banner of “Bt cotton” – a number of quite different debates are being had: over the efficacy of the technology; over the changing nature of agriculture; over the control of agriculture and food by multinationals; over the role of the state in a federal system; over the relevance of regulation in a post-reform economy, and so on. Different actors, deploying different narratives about regulatory policy, join up with different allies at different times. There is no simple story. Yet the sheer complexity of the policy process, and the way this is embedded in the political and social fabric of India, is revealing and important for any discussion about what appropriate policy responses might be to the regulatory dilemmas presented by agricultural biotechnology in the developing world. Despite the advocacy of uniformity and harmonisation in regulatory policy, this paper shows how there clearly can be no one-size-fits-all solution.