The famous (or infamous) command in section 92 of the Australian Constitution that interstate trade and commerce shall be "absolutely free" is only one of the many constitutional restrictions which bedevil organised marketing in Australia. The author, a constitutional lawyer, explains the impact of the Constitution upon organised marketing, and in language accessible to non-lawyers, unravels some of the complexities of the judge-made law of the Constitution. In addition to setting out what the law is, the paper attempts to convey the rationale behind the various constitutional provisions and the reasons behind the diversity of opinion in their interpretation. The paper concludes by examining the prospects for constitutional change.