LOS ANGELES (NYTIMES) - In an aggressive move to defend its Marvel superhero franchises, The Walt Disney Co on Friday (Sept 24) filed a flurry of lawsuits seeking to invalidate copyright termination notices served by artists and illustrators involved with marquee characters like Iron Man, Spider-Man and Thor.

The dispute started in the spring, when a prominent Hollywood intellectual property lawyer, Marc Toberoff, served Marvel Entertainment, which is owned by Disney, with notices of copyright termination on behalf of five clients. They include Lawrence D. Lieber, 89, a comics writer and artist known for his 1960s-era contributions to bedrock Marvel characters.

Toberoff's other clients are the estates of comics illustrators Steve Ditko and Don Heck, and heirs of writers Don Rico and Gene Colan. They are seeking to reclaim rights related to the Marvel characters they had a hand in creating, including Doctor Strange, Black Widow, Hawkeye, Captain Marvel, Falcon, Blade and the Wizard - several of which have become star revenue generators for Disney, appearing in films and television shows, along with a plethora of merchandise.

The reclamation attempts stem from a provision of copyright law that, under certain conditions, allows authors or their heirs to regain ownership of a product after a given number of years. Such efforts turn on whether authors worked as hired hands or produced the material on their own and then sold it to publishers.

The Copyright Revision Act of 1976, which opened the door to termination attempts, bans termination for people who delivered work at the "instance and expense" of an employer.

Disney's lawsuits, filed in federal courts in New York and California, ask judges to toss out the termination notices.

Daniel Petrocelli, a prominent Los Angeles litigator who is representing Disney in the matter, contends that all of the work cited by Toberoff's clients was done at Marvel's instance and expense - an argument that has been successful for Disney in other prominent comics rights cases.

Toberoff could not immediately be reached for comment. His termination notices expressed the intent to regain copyrights to some creations as early as 2023. If successful, Toberoff's clients would receive a portion of profits from new works based on any of the copyrighted material.