Stephen has practised at the forefront of public international law, whether within government or private practice, for more than 20 years. He has advised on cases before the International Court of Justice (ICJ), International Tribunal for the Law of the Sea (ITLOS), European Court of Justice, European Court of Human Rights and multiple domestic courts. He has one of the world’s most prolific and longstanding practices in investment arbitration, having appeared in more than 30 pending and decided cases under the World Bank (ICSID), UNCITRAL and other rules.  He has won some of the largest or most notable investment arbitration awards over recent years.

Before establishing Fietta in 2015, Stephen co-founded the world’s first specialist public international law firm (Volterra Fietta) in 2011. Prior to that, he was a partner specialising in public international law at a leading US and global law firm. Both of those practices were top-ranked at the time. Stephen regularly manages large teams of lawyers (including co-counsel), experts and witnesses in multiple jurisdictions.