Market failure is the predominant justification for regulatory interventions of all kinds. Potential market failure has also been the basic argument behind calls for mandatory labeling of GM foods. However, there is little empirical evidence to suggest that any of the necessary and sufficient conditions for mandatory labeling of GM foods is satisfied. Indeed, it is possible that mandatory GM-food labeling policies installed in some countries could fail all three standard criteria used to justify regulatory intervention. The efficiency of various mandatory labeling regimes has not been sufficiently appraised. Proper methods for measuring consumer behavior and relevant social benefits from mandatory labeling have been ignored and he costs of mandatory labeling policies brushed aside.