Fallout characters and references in their Fallout MMO. It's fairly assured that Judge John Walter felt Interplay owning the Fallout license would allow them to use assets, characters and narrative belonging to the Fallout IP, as Bethesda ridiculously claimed they had no right to them.
However, it's clear that Bethesda's attempt at a restraining order was to drain Interplay's coffers during a long court pre-trial, as "Interplay recently warned investors that the company is on the brink of collapse unless present financial conditions change," according to Develop.
Bethesda had first sued Interplay in 2009, but a US District Court judge denied its motion for a preliminary injunction. The publisher then attempted to say that Interplay and Masthead could not use assets, characters or narrative belonging to the Fallout IP.
Judge Walter shot this down, stated Bethesda “has not demonstrated that it will be irreparably prejudiced” if the restraining order is enacted, and that Bethesda has not shown it is without fault in creating the dispute in the first place.