Skip to main content


Freshfields expands national security team in Washington DC; Former CFIUS Head Brian Reissaus joins as Senior Advisor

Freshfields Bruckhaus Deringer announced today that Brian Reissaus joins the firm as a Senior Advisor, National Security, further reinforcing Freshfields’ leading global foreign investment review and national security capabilities.

Having led the Committee on Foreign Investment in the United States (CFIUS) through its most significant expansion in 30 years, Brian brings exceptionally deep and current insight to Freshfields’ leading global foreign investment and national security practice.  Brian most recently served as Deputy Assistant Secretary for Investment Security Operations at the US Department of Treasury, managing Treasury’s role as chair of CFIUS and leading the development and implementation of US policies regarding inbound and outbound foreign investment. For the first 16 months of the Biden Administration, Brian also served as Acting Assistant Secretary of the Treasury for Investment Security. 

Brian joins a team led by Partner and Head of CFIUS Practice Aimen Mir. Aimen joined Freshfields in 2019 after serving for nearly a decade in leadership roles with the Treasury Department in some of the same roles Brian went on to hold. Between Brian and Aimen, the Freshfields team has managed CFIUS’s review and disposition of almost every transaction that came before the committee in the past 14 years.

Aimen noted “Brian has worked tirelessly over the past several years to build the CFIUS process, executing a mandate to strengthen US national security, while maintaining an open investment environment. Few people have had the impact on the CFIUS process that Brian has had, and he will be an extraordinary resource for clients seeking to understand the CFIUS process, global foreign investment review trends, and the development and implementation of US national security regulatory policy in view of current geopolitical tensions.”

At Treasury, Brian also led the negotiation and implementation of the Foreign Investment Risk Review Modernization Act of 2018 (FIRRMA). Prior to joining the Treasury Department, Brian worked at the US Department of Defense as an Action Officer for the Foreign Ownership, Control or Influence (FOCI) Operations Division at the Defense Security Service where he developed, negotiated, executed and monitored compliance of FOCI mitigation agreements with contractors eligible to hold classified contracts.

Brian adds to Freshfields’ bench of former US national security officials – in addition to Aimen, that includes Beth George (the former Acting General Counsel of the Department of Defense), Brock Dahl (former Deputy General Counsel of the National Security Agency), Kenneth Juster (former Ambassador to India and Deputy Assistant to the President for International Economic Affairs), Colin Costello (former head of the Investment Security Group, Office of Director of National Intelligence), Eric Bruce (former Counselor to the Attorney General) and Timothy Howard (former Chief, Complex Frauds and Cybercrime Unit, Southern District of New York).

About Freshfields Bruckhaus Deringer LLP

Freshfields Bruckhaus Deringer is a global law firm with a long-standing track record of successfully supporting the world's leading national and multinational corporations, financial institutions and governments on groundbreaking and business-critical mandates. Our 2,800-plus lawyers deliver results worldwide through our own offices and alongside leading local firms. Our commitment, local and multinational expertise, and business know-how means our clients rely on us when it matters most.

Freshfields is ranked by Chambers Global in Band 1 across the six areas of antitrust, corporate/M&A, litigation, international arbitration, tax, and public international law. For more information visit