The "Stop Fentanyl Money Laundering Act of 2025" empowers the Secretary of the Treasury to implement special measures against foreign financial institutions, transactions, or accounts identified as primary money laundering concerns related to illicit fentanyl and narcotics financing. These measures can compel domestic financial institutions to take specific actions to counter such illicit financial flows. The bill incorporates existing legal frameworks for penalties, injunctions, and the handling of classified information in relation to these designations. To enhance financial institutions' ability to combat illicit financing, the bill directs the Financial Crimes Enforcement Network (FinCEN) to update and issue a new advisory within one year. This advisory will focus on identifying Chinese professional money laundering facilitating fentanyl and synthetic opioid trafficking, integrating previous relevant advisories. Furthermore, FinCEN must issue guidance within 180 days for U.S. financial institutions on filing suspicious transaction reports concerning narcotics trafficking by transnational criminal organizations . The Director of FinCEN is also required to prioritize research into suspicious activity reports that indicate a connection to narcotics trafficking and brief Congress on the effectiveness of the new guidance. Finally, the Comptroller General, in collaboration with the Treasury Department and other agencies, must provide an unclassified report to Congress within 360 days. This report will analyze lessons learned from previous drug crises, such as the crack cocaine crisis, to inform strategies for mitigating the targeting of victims and the negative impacts of the ongoing opioid crisis.