Administrative agencies have undertaken an increasingly substantial role in policymaking. Yet the influence-seeking that targets these agencies remains poorly understood. Reporting exceptions under the Lobbying Disclosure Act allow many of the most powerful advocates to characterize their activity as lawyering, not lobbying, and thereby fly under the radar. Using agency-generated records on lobbying activity, financial reporting, and personnel databases specific to lawyers, as well as LinkedIn, we describe a vast subterranean world of regulatory influence-seeking that the social-science literature has (mostly) ignored. Regulatory lobbying is systematically different from legislative lobbying. It involves different kinds of people and different lobbying firms that bring specific forms of expertise and distinct networks. Our key findings about how regulatory lobbying differs include the following: (1) the regulatory lobbying sector is highly segregated from the reported lobbying sector, with many regulatory advocates failing to consistently register or report earnings commensurate with their activity level, (2) the number of unregistered regulatory advocates working on the implementation of the Dodd-Frank Wall Street Reform Act plausibly exceeds 150% of the registered lobbyists working on that law, (3) the most effective regulatory lobbyists and law firms involved with regulatory lobbying have incomes that dramatically outpace leading reported lobbying firms (which are also mostly law firms), and (4) back-of-the-envelope calculations and more sophisticated decomposition regressions imply that aggregate expenditure on lawyer-lobbying is several multiples of reported lobbying spending. We introduce the case of a particular lawyer-lobbyist and provide a theoretical discussion to situate and contextualize these findings. Collectively, this work opens a window into neglected domains of politics and reveals an important and understudied form of political inequality.