Federal systems enable the minimisation of cross-border externalities and the exploitation of economies of scale. Because of the limited information or foresight of the founding fathers, various inefficiencies arise over time. One means of addressing these is "constitutional trade" between State and federal governments. In this article, I explore the effect of constitutional interpretation on these trades, illustrated by reference to the decision in Re Wakim. After criticising the High Court's decision, I discuss two means of addressing the case's inefficiency, including Commonwealth legislation under the corporations power, and enabling the parties to corporate contracts to take responsibility for forum selection.