“Impossibility of performance is a common law defense to an action for failure to perform an obligation. Aspects of the defense have been codified in California as discussed herein. In early California cases, true and complete impossibility, sometimes spoken of as literal or physical impossibility, was required and mere unforeseen difficulty or expense would not constitute impossibility even if extraordinary. More recent decisions recognize circumstances in which extraordinary expense or difficulty will constitute impossibility even if the performance of the contract is not, in fact, utterly impossible.”
[California Affirmative Defenses [certain citations omitted]]
