In the comics it was Batman's enemy Ra's al Ghul that got ahold of Batman's secret files regarding his Justice League teammates and their weaknesses instead of Vandal Savage.
Phil Morris reprises the role of Vandal Savage from Justice League (2001). Morris also played John Jones aka The Martian Manhunter on the television series Smallville (2001).
Kevin Conroy (Batman), Tim Daly (Superman), Susan Eisenberg (Wonder Woman), Carl Lumbly (Martian Manhunter), Phil Morris, Olivia d'Abo (Star Sapphire), and Alexis Denisof all reprise their previous television roles for this film. Additionally, Michael Rosenbaum, who previously voiced Flash Wally West, returns to voice Flash Barry Allen.
While most of the film material is completely original, the plotline of Batman developing countermeasures against his Justice League teammates as a deterrent, only to have the plans stolen and used against the Justice League is based off the 2000 JLA storyline "Tower of Babel".