Walt Disney Co. is suing the estates of former Marvel Comics superheroes artists to determine who owns the rights to the characters, including Iron Man and Spider-Man, according to media reports.

Marvel, owned by Disney since 2009, filed multiple complaints in federal court in New York and California to invalidate copyright termination notices the former artists’ estates served against the Burbank entertainment and media giant early this year, according to the Los Angeles Times.

The newspaper said that one of the defendants is Lawrence D.  Lieber, the brother of the late Stan Lee, long the public face of Marvel. Lieber, 89, was hired by Marvel in the late 1950s to write stories featuring the likes of Iron Man, Thor and Ant-Man.

Marvel, filing its lawsuits under the name Marvel Characters Inc., said in court documents that because Lieber and the others toiled as “work for hire,” they have no legal ownership rights to the characters they worked on, the Times story said.

“Any contributions Lieber made were at Marvel’s instance and expense, rendering his contributions work made for hire, to which the Copyright Act’s termination provisions do not apply,” Marvel said in one of its complaints, according to the Times.

Dan Petrocelli, the attorney representing Marvel in the case, reiterated the company’s argument in an emailed statement received by the Times.

“Since these were works made for hire and thus owned by Marvel, we filed these lawsuits to confirm that the termination notices are invalid and of no legal effect,” Petrocelli said in the email.

Marc Toberoff, the attorney representing Lieber and the estates of artists Steve Ditko, Don Heck, Don Rico and Gene Colan in similar claims over Marvel character rights, said that Disney was calling the shots in the lawsuits.

“At the core of these cases is an anachronistic and highly criticized interpretation of ‘work-made-for-hire’ under the 1909 Copyright Act that needs to be rectified,” Toberoff said in a statement to the Times.

Shares in Disney (DIS) closed down 25 cents or a fraction of a percent, to $176 on the New York Stock Exchange.