­A three-judge panel unanimously ruled that the heirs of Superman's co-creator, Jerome Siegel, must abide by a letter written by the family's attorney in 2001, accepting Warner Bros.' offer for their 50 percent share of Superman. Despite the fact that the letter was never formalized into a contract, according to the appeals court it was still binding.

"Statements from the attorneys for both parties establish that the parties had undertaken years of negotiations, that they had resolved the last outstanding point in the deal during a conversation on Oct. 15, 2001, and that the letter accurately reflected the material terms they had orally agreed to on that day," Judge Stephen Reinhardt wrote for the panel, AP reported.