Kirby's heirs have no claim on properties created by the artist including the Fantastic Four and the Hulk, New York federal judge Colleen McMahon has declared.
She ruled that the 1960s characters were strictly created as work-for-hire and therefore the property of the publisher, reports Comic Book Resources.
"At the outset, it is important to state what this motion is not about," said McMahon in a 50-page written judgment.
"Contrary to recent press accounts, this case is not about whether Jack Kirby or Stan Lee is the real 'creator' of Marvel characters, or whether Kirby (and other freelance artists who created culturally iconic comic book characters for Marvel and other publishers) were treated 'fairly' by companies that grew rich off the fruit of their labour."
Judge McMahon continued: "It is about whether Kirby's work qualifies as work-for-hire under the Copyright Act of 1909... If it does, then Marvel owns the copyright in the Kirby works, whether that is 'fair' or not. I
"If it does not, then the Kirby heirs have a statutory right to take back those copyrights, no matter the impact on recent corporate acquisition or on earnings from blockbuster movies made and yet to be made."
The rights to the Superman property remain the subject of an ongoing legal battle between DC Comics and the heirs of creators Jerry Siegel and Joe Shuster.