For lawyers accustomed to working under U.S. attorney-client privilege, the raid by German prosecutors on Jones Day’s Munich offices and the legal battle over whether they can use the seized materials is hard to comprehend.

Hired by Volkswagen AG to oversee an internal investigation into the German carmaker’s use of secretive software to cheat emissions tests, Jones Day in March found its local outpost overrun by law enforcement agents, who left with more than 150 lever arch folders and USB sticks full of electronic files relating to the so-called “dieselgate” scandal.