A judge has ruled that a former agreement disqualifies the heirs of co-creator Joe Shuster from pursuing the rights of his legendary creation.
The brother and sister of Shuster were judged to have relinquished their claim in return for increased royalties that they were given in 1992.
The family had argued that, under changes made to the copyright law in 1999, the copyright agreement with DC Comics and its owner Warner Bros could be cancelled and reclaimed.
"We respectfully disagree with its factual and legal conclusions, and it is surprising given that the judge appeared to emphatically agree with our position at the summary judgment hearing," said a Shuster family lawyer in a statement.
Superman co-creator Jerry Siegel's daughter Laura Siegel recently published an open letter in which she said she would not be "bullied or deterred".
Warner Bros has declined to comment on the case.