The objective of this paper is to present a legal theory of agency selection. The theory posits why certain legal forms of agency are chosen when agencies are created by the executive branch of government. At the core of the theory is the idea that the executive branch chooses agency forms that strike a politically optimal balance between maximising its control while minimising its legal and political accountability for agency activities. This optimal balance is determined on an issue by issue basis. As such, the rise of the regulatory state has provided a means by which the executive branch of government has been able to strategically choose to divest itself of and minimise its legal accountability for the administration of government while, at the same time, maintaining effective political control of the administrative arm of government.