Law.com has an interesting follow-up to the surprise settlement last week in the five-year-old legal battle between Marvel and Jack Kirby's heirs, noting that the larger copyright issue at its center remain unresolved.

The children of the legendary artist filed 45 copyright-termination notices in September 2009, seeking to reclaim what they saw as their father’s stake in such Marvel characters as the Avengers, the X-Men, the Fantastic Four and the Incredible Hulk. Marvel, joined by its then-new parent company Disney, responded with a lawsuit, setting the dispute down a path that ultimately saw the Second Circuit Court of Appeals affirm Kirby's contributions to the publisher between 1959 and 1963 were "work for hire," and therefore not subject to copyright termination.

Under a clause in the 1976 U.S. Copyright Act, which extended the duration of copyright, authors or their heirs can reclaim rights transferred before 1978 after a period of 56 years. However, if a work is determined to be "for hire," meaning it was created by an employee as part of his employment or specially commissioned as part of a larger work, then the publisher (or movie studio, record label, etc.) owns the copyright, and it is not subject to termination.

The problem, Stanford Law School Prof. Paul Goldstein tells Law.com, is that determining whether something was made "for hire," particularly older works, is “extraordinarily difficult.”

The Kirby heirs insisted the artist was an independent contractor who worked from home, provided his own supplies and received no benefits. However, he Second Circuit, using its frequently criticized "instance and expense" test, found that because Marvel assigned and approved projects and paid a page rate, Kirby's contributions were indeed "for hire."

The Kirbys took aim at the Second Circuit's definition of work for hire in their petition to the U.S. Supreme Court, which drew support from the likes of Hollywood guilds and a former director of the U.S. Patent and Trademark Office, demonstrating the potentially far-reaching ramifications of the dispute. However, the 11th-hour settlement announcement arrived just ahead of a Supreme Court conference on Monday to determine whether to review the case -- meaning the Second Circuit's finding stands.

So the gray area surrounding work for hire before 1978 remains, although experts say given that 56-year window -- or 35 years for copyrights transferred after 1979 -- it's only a matter time before another case, more likely to involve a musician/songwriter than a comics artist, makes its way to the Supreme Court, requiring the justices to weigh in.

As Kirby family attorney Marc Toberoff told Law.com, "“At some point there will be another case like this."