The Stop Trading on Congressional Knowledge Act of 2012 (the “STOCK Act”) affirms that members of Congress are not exempt from insider trading prohibitions. Legal scholars, however, continue to debate whether the legislation was necessary. Leveraging recent scholarship on fiduciary political theory, some commentators contend that because members owe fiduciary-like duties to citizens, to their fellow members, and to Congress as an institution, existing insider trading theories already prohibited them from using material nonpublic information for personal gain. These arguments, while plausible, are incomplete. They rely on broad conceptions of legislators as fiduciaries, but provide scant evidence that members violate institutional norms when...