The history of insider trading law is a tale of administrative usurpation and legislative acquiescence. Congress has never enacted a prohibition against insider trading, much less defined it. Instead, the SEC has led in defining insider trading, albeit without the formality of rulemaking, and subject to varying degrees of oversight by the courts. The reason why lies in the deference that the Supreme Court gave to the SEC in its formative years. The roots of insider trading law are commonly traced to the SEC’s decision in Cady, Roberts & Co. Cady, Roberts was only made possible, however, by the Supreme Court’s decisions in SEC v. Chenery Corp., its first brush with insider trading under the federal securities laws. In Chenery I, Justice Fe...