Labelling of genetically modified foods is a contentious issue and internationally there is sharp division on whether such labels ought to be mandatory. This debate has reached India where the government has proposed mandatory labels. Mandatory labelling aims to provide greater information and correspondingly more informed consumer choice. However, even without such laws, markets have incentives to supply labels. So can mandatory labelling achieve outcomes different from the voluntary type? The paper argues that this is not the case in most situations. It goes on to explore the special set of circumstances, where mandatory labels make a difference to outcomes. If these outcomes are intended, mandatory labelling is justified; otherwise not. Although the Indian context provides the motivation, the core arguments given are general and applicable to other country contexts as well.