(CBR) Although the attorney representing the heirs of Superman creators Jerry Siegel and Joe Shuster had vowed they were “prepared to go the distance” in their legal battle with DC Comics, they appear to have reached the end of the road. Of course, that’s been said a few times before.

As Deadline reports, in a 2-1 vote the Ninth Circuit on Thursday tied up the loose ends in what it describes as “the long-running saga regarding the ownership of copyrights in Superman — a story almost as old as the Man of Steel himself,” reaffirming an October 2012 ruling that the Shuster estate is prevented from reclaiming the artist’s stake in the character by a 20-year-old agreement with DC.

“We are obviously very pleased with the court’s decision,” DC’s parent company Warner Bros. said in a statement.

That lower-court decision, which was appealed in May, dealt with a 1992 deal in which the Shuster estate relinquished all claims to Superman in exchange for “more than $600,000 and other benefits,” which included paying Shuster’s debts following his death earlier that year and providing his sister Jean Peavy and brother Frank Shuster with a $25,000 annual pension. In October, U.S. District Judge Otis D. Wright found that the agreement invalidated a copyright-termination notice filed in 2003 by Shuster’s nephew Mark Peary.

Less than three months later, the Ninth Circuit overturned a 2008 decision that granted the Seigel heirs his 50-percent share of the copyright to the first Superman story in "Action Comics" #1, effectively giving DC full ownership of the character. That was followed in April by Wright’s ruling that Superboy also belongs to the publisher, an issue left unresolved by the appeals court’s decision.

However, attorney Marc Toberoff insisted the judge “committed clear error” in the matter of the Shuster estate’s 1992 deal by finding that the one-page pension agreement precluded the family from exercising its termination rights under U.S. copyright law. What’s more, he asserted, Peavy and Frank Shuster had no termination rights to exercise in 1992 because Shuster’s stake in Superman had been assigned to DC in 1938, and the publisher still owned the rights at the time of the pension agreement.

In his dissent on Thursday, Judge Sidney Runyan Thomas agreed, at least in part, noting that because Shuster’s estate hadn’t entered probate at the time of the 1992 agreement, neither the artist’s sister nor brother had the authority to “dispose of Joe’s copyright interests.”

The next step could be a request for a hearing before the Ninth Circuit’s full bench, but Toberoff has expressed a willingness to take the battle to the Supreme Court. However, it’s likely the three-judge panel was the final fight for the Shusters.

For the Siegel family, there’s still a possibility of breach-of-contract claims against DC, although even that may run afoul of statute of limitations. After the Ninth Court in January found they had indeed accepted a multimillion-dollar offer in 2001 from DC, the heirs tried a new strategy: If there was an agreement — it called for the publisher to retain all rights to Superman (and Superboy and The Spectre) in exchange for $3 million in cash and contingent compensation worth tens of millions — then DC had failed to perform. (That explains the recent addition of the line “By Special Arrangement with the Jerry Siegel Family” to the credits of any DC title featuring Superman, a stipulation of the 2001 agreement. ROBOT 6 contributor Tom Bondurant also noted that Superboy is now “created by Jerry Siegel,” while Supergirl is “based on characters created by Jerry Siegel and Joe Shuster.”)

But Judge Wright asserted, on at least two occasions, that any contract dispute that might arise is a matter for state, not federal, courts.

Cover for 'Action Comics' #1 featuring the debut of Superman

Copyright © 2014 Comic Book Resources. Reprinted with permission. All rights reserved.