Mixed Arbitral Tribunals, 1919–1930:
An Experiment in the International Adjudication of Private Rights

23–24 April 2020

Session of the German–Polish Mixed Arbitral Tribunal in Paris, February 1925.
(National Digital Archive, Poland)

The creation of a system of Mixed Arbitral Tribunals (MATs) was a major contribution of the post-WWI peace treaties to the development of international adjudication. Numerically speaking, the 36 MATs were undoubtedly the busiest international courts of the interwar period. Taken together, they decided on more than 70,000 cases, mostly covering private rights. This caseload is even more impressive if one considers that their existence generally did not exceed 10 years, as most of the MATs were discontinued pursuant to the 1930 Young Plan. The MATs are similarly remarkable from a procedural point of view. First, their respective rules of procedure were so detailed that contemporaries described them as 'miniature civil procedure codes'. Second, in a departure from most other international courts and tribunals, they also allowed individuals whose rights were at stake to become involved in the proceedings before them. Although the MATs failed to produce a universally consistent body of case-law, their collection of published decisions was a major source for legal doctrine in the 1920s and 1930s and remains of interest for international lawyers today. The MATs themselves served as a source of inspiration for other international and supranational courts and tribunals, including the European Court of Justice. Their example might similarly inspire potential future negotiations over institutionalized investment tribunals.

And yet, like many other international 'experiments' of the interwar period, the MATs are often barely mentioned in post-WWII accounts of international law. Despite (or perhaps because of) the amount of cases they handled and the vastness of archival records they generated, they have not given rise to a single major monograph after 1945.

By organizing a conference specifically dedicated to the MATs and their impact on international adjudication of private rights, the Max Planck Planck Institute Luxembourg for Procedural Law would like to provide researchers with the opportunity to shed new light on this often overlooked chapter in the history of international law.