Janet Yellen

Led the U.S. Treasury during a period when the Office of Foreign Assets Control (OFAC) moved to designate Tornado Cash-related addresses and services as subject to sanctions. Under the Treasury's senior leadership, the department publicly linked the mixer to illicit cyber‑theft proceeds and designated specific addresses and tools, a policy action that directly changed compliance obligations for U.S. financial institutions and cryptocurrency service providers. The designation process and Treasury statements guided exchanges, custodians and analytics firms to delist, flag or restrict transactions involving Tornado Cash‑related addresses. That cascade materially affected on‑chain liquidity for the protocol and the practical ability of users to move funds through custodial rails, as many service providers adjusted monitoring and sanctions‑screening rules to align with Treasury guidance. Public leadership and policy framing also shaped international regulatory conversations and law‑enforcement cooperation, prompting arrests and prosecutions in allied jurisdictions. The Treasury's explicit targeting of mixer infrastructure established a precedent for enforcement against protocol‑level services and influenced subsequent rule‑making and compliance approaches in the crypto sector.