Securities regulation has traditionally focused on encouraging truthful disclosure that facilitates the accurate pricing of securities. A typical securities fraud claim under the primary antifraud provision, Rule 10b-5, must thus point to a misrepresentation or omission that is material to investors. At the same time, it is undeniable that Rule 10b-5 has been extended to conduct that does not fit this traditional conception of fraud, most notably insider trading. This Article shows that such deviations have become more common as Rule 10b-5 has increasingly become concerned with the problem of unjust enrichment. In numerous areas, the courts have applied Rule 10b-5 to deceptive conduct that is not directed at the market or investors but unjustly enriches some individual. Surprisingly, the unjust enrichment principle has functioned not only as an expander of liability but also as a limit. More and more, securities fraud class actions directed at market-distorting misrepresentations may only proceed if insiders have been enriched by the misrepresentation. The rise of the unjust enrichment principle demonstrates that securities regulation is not only concerned with the economic value of market efficiency but also is significantly influenced by public values. Securities regulation is guided by an evolving principle that sets some limits on the ability to extract wrongful gains from the securities markets. Though unjust enrichment is undeniably a concern of Rule 10b-5, it should be a second-order concern subordinate to the first-order concern of efficient markets.
