Explains The Hollywood Reporter, "The nasty dispute between Warners and the heirs of co-creators Jerry Siegel and Joe Shuster stems from a 2008 court ruling that the Siegels are entitled to terminate the copyrights to some—but not all—of Superman’s defining characteristics, such as his costume, Clark Kent and his origin story, as described in the first editions of Action Comics. Throughout years... it has never been determined whether the Shusters and Siegels can take back other key elements of the Superman mythology, such as Lex Luthor and Kryptonite."
Which creates a challenge for lawyer Marc Toberoff and the Siegel and Shuster heirs to try and take their rights elsewhere or force the studio into making a settlement offer. It is Toberoff's hope that the appeal court will determine which aspects of Superman are owned by whom.
”It’s cutting to the chase,” Toberoff tells THR. “It is widely recognized that Judge Larson’s rulings on summary judgment largely favored the Siegels in upholding the validity of their termination as to Action Comics No.1, containing the core Superman format and characters.”
Warners, of course, sees things differently: "DC Comics and Warner Bros. are fully confident that the trial court's rulings against the Siegels are correct and will be affirmed on appeal.”
For Warners, while the studio is free to produce Man of Steel, depending on what the court says could theoretically jeopardize future films. Though one cannot imagine a scenario in which, if the courts should rule in Siegel and Shuster's favor, a deal won't be worked out between both parties for future versions of Superman.