Marik String is an international and national security lawyer advising clients on matters at the intersection of national security, cross-border investment, international trade and disputes, and global public policy. He returned to the firm in 2021 after serving in senior government roles at the US Department of State, US Department of Defense and US Senate, including as Acting Legal Adviser (General Counsel) of the Department of State.  

He is an authority on US sanctions, export controls, anti-boycott, and other national security and foreign policy regulations administered by the US Treasury Department’s Office of Foreign Assets Control (OFAC), State Department’s Directorate of Defense Trade Controls (DDTC) and Commerce Department’s Bureau of Industry and Security (BIS). He represents clients before the Committee on Foreign Investment in the United States (CFIUS) and Defense Counterintelligence and Security Agency (DCSA) in connection with international investments and mergers, corporate security clearances, classified government contracting, and the structuring of national security agreements to mitigate foreign ownership, control or influence. 

Mr. String also represents clients in connection with sensitive national security investigations by Congress and the Executive Branch involving cybersecurity, defense, intelligence and foreign relations issues. He has deep knowledge and experience with international arbitration and international litigation in US courts involving the Foreign Sovereign Immunities Act (FSIA), official and diplomatic immunity, and the extraterritorial application of US law. 

From 2019–2021, he was Acting Legal Adviser of the US Department of State, serving as the chief legal officer of the Department and principal legal adviser to Secretary of State Michael Pompeo. While managing the Office of the Legal Adviser’s 375 attorneys and staff, he supervised the United States’ international claims and litigation portfolio and served as Agent of the United States in cases before the International Court of Justice (ICJ) and Iran-US Claims Tribunal. He argued before the ICJ in Iran v. United States—Alleged violations of the 1955 Treaty of Amity and was one of four members of the US National Group of the Permanent Court of Arbitration (PCA), the body that nominates ICJ judges. He was a key adviser on the US-Sudan bilateral claims agreement that resolved terrorism-related claims arising from the 1998 East Africa embassy bombings and the 2000 attack on the USS Cole. During his tenure, he assisted in drafting every major Executive Order affecting international sanctions, trade and investment.

Previously, Mr. String was Acting Assistant Secretary and Deputy Assistant Secretary of State for Political-Military Affairs (2018-2019), supervising the US Government’s $200 billion annual defense trade portfolio and the bureau’s 400 officers. He managed the Directorate of Defense Trade Controls and all export control functions under the International Traffic in Arms Regulations (ITAR), including export control reform, voluntary disclosures, debarments and civil penalties. He previously served as Senior Adviser to Deputy Secretary of State John J. Sullivan (2017-2018) and Deputy Chief Counsel and Senior Professional Staff Member for European and Eurasian Affairs on the US Senate Committee on Foreign Relations under Senator Richard G. Lugar (2006-2013). Mr. String is a commissioned officer in the US Navy Reserve.

He has been a scholar affiliated with The Atlantic Council and Aspen Institute Berlin.  His commentary on legal and national security issues has appeared in, among other outlets, The Wall Street Journal, Foreign Affairs and Bloomberg.

Insights & News


  • Education

    • JD, Georgetown University Law Center

      magna cum laude Editor, The Georgetown Law Journal, Global Law Scholar
    • MA, University of Vienna

      Fulbright Scholar
    • BA, University of Notre Dame

      magna cum laude John Sheehan Prize
  • Admissions

    • District of Columbia

    • New York

  • Government Experience

    • Department of State

      Acting Legal Adviser
    • Department of State

      Acting Assistant Secretary, Deputy Assistant Secretary for Political-Military Affairs
    • Department of State

      Senior Adviser to Deputy Secretary of State
    • Federal Legislative Branch

      US Senate

      Deputy Chief Counsel and Senior Professional Staff Member for European and Eurasian Affairs, Senator Richard Lugar (R-IN), Senate Foreign Relations Committee



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