Matthias is one of the world’s most experienced arbitration lawyers and is hailed as one of the “most in demand arbitrators” in Chamber’s Global, 2023, and Chamber's Europe, 2025, and is a member of the ICSID panel of arbitrators, regularly appointed by parties and major arbitral institutions (including the ICC, Swiss Arbitration Centre, ICSID, LCIA, SCC, DIAC, VIAC and Danish Institute of Arbitration).

He has three decades of practice representing parties in complex international disputes. A “Leading Individual” and “a prominent name for investor-state arbitrations”, Legal 500, Matthias has acted as counsel in over 200 arbitrations and ADR proceedings under various arbitration rules (ICC, ICSID, Swiss Rules, LCIA, UNCITRAL, VIAC, CAS, SCC), governed by both civil and common law procedural and substantive laws. 

In addition, he represents parties in arbitration-related court proceedings, especially in the challenge of commercial and investment treaty arbitral awards before the Swiss Supreme Court.