Leuphana Scientists Contribute to Germany's Success Before an International Arbitration Tribunal
Delays in Offshore Wind Farms in the North Sea
2026-10-29 Three legal scholars from Leuphana served as expert witnesses: In an international arbitration proceeding concerning delayed offshore wind farms in the North Sea, the Federal Republic of Germany was able to fend off claims for damages totaling more than 350 million euros. An international arbitration tribunal dismissed the energy company’s claim in its entirety in May 2026. This marked the first time Germany had fully prevailed in an international investment protection proceeding. Prof. Dr. Jelena Bäumler, Prof. Dr. Thomas Schomerus, and Prof. Dr. Jörg Terhechte - who passed away in 2024 - served as legal experts for the Federal Republic of Germany in both the oral and written proceedings and faced cross-examination by the opposing party in London.
The Energy Charter Treaty is an international agreement that protects private investments in the energy sector. On this basis, various companies had sued Germany for several hundred million euros. They argued that changes to national law had hindered their investments in offshore wind farms in the North Sea and thus violated their rights. In the case “Mainstream Renewable Power Ltd and others v. Federal Republic of Germany (ICSID Case No. ARB/21/26),” the three-member arbitral tribunal—composed of Wendy Miles, Antolín Fernández Antuña, and Charles Poncet—confirmed Germany’s legal position and concluded that the changes to German law did not constitute a violation of the investors’ rights protected under the Energy Charter Treaty. “States need leeway, especially during major transformation processes such as the energy transition; not every change in the legal landscape automatically constitutes a violation of investor rights,” explains Thomas Schomerus. Following the two-week oral hearing in London, during which there was intensive collegial cooperation among the Leuphana faculty members, the tribunal dismissed the claim in its entirety.
This case serves as a prime example of how legal expertise informs the practice of international dispute resolution, as well as the significance that well-founded legal research can have for assessing complex issues at the intersection of national constitutional law, investment protection, government regulation, and the energy transition. The scholars’ expertise in national energy law and constitutional law supported Germany’s argument that the legislative changes did not constitute a violation of protected investor rights.
Implications for Energy Policy
The Energy Charter Treaty protects international investments in the energy sector, but has faced criticism for years because it can limit governments’ ability to act in the energy transition. Germany, the EU, and numerous other EU member states have therefore withdrawn from the treaty. Nevertheless, due to a so-called sunset clause, investors can still assert claims for many years after withdrawal. The Mainstream case demonstrates that international investment arbitration proceedings will continue to play a significant role in energy policy in the future.
The decision, the so-called “Award”,is available in its entirety at: https://icsid.worldbank.org/cases/case-database/case-detail?CaseNo=ARB/21/26