On January 17, 2020, the U.S. Department of the Treasury issued the final regulations to implement the Foreign Investment Risk Review Modernization Act of 2018 (FIRRMA), legislation that significantly expanded the jurisdiction of the Committee on Foreign Investment in the United States (CFIUS). Though the final regulations largely retain the substance of the 2019 proposed regulations, there are several key differences. In particular, the regulations include an interim rule establishing a new definition for “principal place of business,” which will be helpful for foreign-domiciled investment funds that are ultimately controlled from the United States by U.S. persons. The pilot program that imposed a mandatory declaration filing requirement for certain transactions involving critical technologies has been incorporated into the final regulations. However, the final regulations exempt certain investors from the mandatory CFIUS, including U.S.-owned and controlled investment funds, investors acquiring critical technologies that are only controlled for encryption reasons, excepted investors, and entities already subject to foreign ownership, control, or influence (FOCI) mitigation. Additionally, CFIUS has published the initial list of excepted foreign states -- which includes only Australia, Canada, and the United Kingdom -- and marginally liberalized the excepted investor provisions that allow filing exemptions for non-control transactions involving certain entities closely tied to the excepted foreign states.