Few issues in securities law have excited the popular imagination and generated scholarly interest like insider trading. Yet, a simple but foundational question about insider trading law has received relatively little scholarly attention: Does insider trading law actually influence the amount of insider trading that occurs? This Article tackles this question in the context of one of the highest-profile changes in insider trading law in decades — the Second Circuit’s seminal 2014 decision in United States v. Newman, which substantially weakened insider trading law concerning so‑called “tippee” liability. The Article’s empirical approach exploits Newman’s change in law to evaluate the effects of changes in insider trading law on insider trading. The Article focuses on insider trading in advance of mergers announced in periods before and after Newman and, for its measure of the extent of insider trading, uses the run‑up in the stock price of the merger target in advance of the merger’s public announcement. Based on that measure, the Article finds that Newman had a dramatic effect on insider trading, with significantly greater insider trading occurring after Newman than before, thereby providing strong empirical evidence that insider trading is responsive to changes in insider trading law. The Article provides the first empirical analysis of whether a specific judicial change in insider trading law can influence the amount of insider trading beyond just the trading of corporate insiders. The Article’s empirical findings advance our understanding of the functioning of securities law and inform important policy debates concerning insider trading.