AGG Expands International Dispute Resolution Practice With Diana Tsutieva and Mark Clodfelter

WASHINGTON, D.C., June 9, 2026 – Arnall Golden Gregory LLP (AGG) welcomes Diana Tsutieva and Mark A. Clodfelter to the firm’s Washington, D.C. office and International Dispute Resolution practice. Diana joins as practice chair and Mark joins as senior counsel. Together, they bring extensive experience representing sovereign states, multinational companies, and investors in international disputes and cross-border matters.

“Diana and Mark significantly strengthen AGG’s international disputes platform,” said Michael E. Burke, chair of AGG’s International practice and administrative partner of the firm’s Washington, D.C. office. “Their experience handling investor-state, commercial, and sovereign disputes complements our international capabilities and expands the sophisticated counsel we provide clients navigating complex cross-border matters.”

Diana Tsutieva’s Practice Leadership and Client Representation

Widely recognized for her work, Diana joins as chair of AGG’s International Dispute Resolution practice. She focuses on investor-state arbitration, commercial arbitration, public international law matters, and cross-border litigation. She represents clients in proceedings before leading arbitral institutions, including ICSID, UNCITRAL, and the ICC, involving energy, mining, financial services, healthcare, waste management, telecommunications, and environmental claims.

Diana has successfully defended European, Eurasian, and Latin American states in investor-state arbitrations, resulting in jurisdictional victories, complete victories on liability, and reductions of claimed damages by more than 90%. She has also represented clients in enforcement proceedings in U.S. federal courts under the Foreign Sovereign Immunities Act and the New York Convention. Diana sits as an arbitrator in international commercial proceedings and advises clients on a wide range of public international law matters, including investment treaty reform, international trade, and human rights.

“AGG’s international platform provides a strong foundation for growing the International Dispute Resolution practice that serves clients facing increasingly complex cross-border challenges,” Diana said. “I am excited to build on the firm’s international capabilities and support clients across jurisdictions and industries. And having Mark Clodfelter join my team, after more than a decade working together with a proven record of success, reflects AGG’s commitment to a practice that can handle the most complex international disputes.”

Diana is active in the international disputes community through her involvement with the ICC Young Arbitration and ADR Forum, American Society of International Law, ABA Section of International Law, and the American-Uzbek Law Association. Diana is a frequent speaker and author on international arbitration, investment treaty reform, and emerging issues at the intersection of international law and climate change. She has been recognized in Who’s Who Legal: Arbitration and Lexology: Arbitration as a Future Leader, earning “widespread international praise” for her work on complex investment and commercial arbitration matters.

Diana earned her LL.M. from the University of Paris I: Panthéon-Sorbonne in European Union & French Laws, her J.D. from Rutgers Law School, and her B.A. from Cornell University in comparative literature.

Mark A. Clodfelter’s International Dispute Experience

Mark brings more than 40 years of experience in international commercial disputes. He has served as counsel and arbitrator before leading tribunals and arbitration forums, including ICSID, the Permanent Court of Arbitration (PCA), the ICC, the Stockholm Chamber of Commerce (SCC), the American Arbitration Association (AAA), and tribunals operating under the UNCITRAL Arbitration Rules, the U.N. Compensation Commission, and the Iran-U.S. Claims Tribunal.

He served for seven years as the U.S. State Department’s Assistant Legal Adviser for International Claims and Investment Disputes, where he led matters involving the protection of U.S. citizens and businesses abroad and represented the United States in international arbitration proceedings. His experience spans the representation of seven sovereign states, as well as individual and corporate investors, and in investor-state, state-to-state, and commercial disputes.

“I have had the privilege of working alongside Diana for many years and have seen firsthand the caliber of counsel she provides clients,” Mark said. “Her leadership, together with AGG’s strong international platform, presents a unique opportunity to further strengthen the firm’s international disputes capabilities and client service.”

A former White House Fellow and recipient of the Presidential Rank Award for Meritorious Service, Mark has been recognized by Washingtonian magazine as one of Washington, D.C.’s leading international lawyers. He has also received the American Bar Association’s Award for Outstanding Performance by an International Law Office. He has written and spoken extensively on international arbitration issues and taught international commercial arbitration for seven years in the graduate program of the Georgetown University Law Center in Washington D.C.

Mark earned his J.D. from the University of Michigan Law School, and both his M.A. in Political Science and his B.A. in Russian and East European Studies from the University of Michigan. He is admitted to the bar in the District of Columbia and Michigan.

ABOUT ARNALL GOLDEN GREGORY LLP

Arnall Golden Gregory (AGG) is an Am Law 200 law firm with offices in Atlanta and Washington, D.C. Our client-service model is rooted in taking a “business sensibility” approach of fully understanding how our clients’ legal matters fit into their overall business objectives. Our transaction, litigation, regulatory, and privacy counselors serve clients in healthcare, real estate, retail, technology, fintech/payment systems, global commerce/global mobility, life sciences, logistics and transportation, government investigations, and government contracts. With our rich experience and know-how, we don’t ask “if,” we figure out “how.” Visit us at www.agg.com.