Abstract
Carbon emissions trading markets are unrealistically treated as either voluntary or mandatory. Yet most trading incorporates some voluntary and some regulatory features and there is developing interaction. Diverse emissions trading markets include an array of voluntary aspects. Voluntary features of trading should be evaluated on their own merit according to the context of the scheme in question.
Acknowledgements
With thanks to Markus Gehring for supervising the Masters degree from which this article is taken, to Sue Miller for enjoyable work on the UK Climate Change Act and to two reviewers and the editor for helpful comments.