Buck Stops Here Act This bill allows the Department of the Treasury to impose restrictions on an entity or activity determined to be of primary money-laundering concern in connection with illicit fentanyl trafficking. Specifically, if Treasury determines that a foreign financial institution, class of transaction, or type of account is of such concern, Treasury may (1) require domestic financial institutions and agencies to take special measures, such as reporting certain financial transactions involving that entity or activity; or (2) prohibit, or impose certain conditions upon, the transmittal of funds involving any domestic financial institution or agency and that entity or activity.