Final answer:
The doctrine of frustration discharges a contract in cases like war, legal changes, or destruction of necessary subject matter and is not applicable when the event was foreseeable, provided for in the contract, or assumed as a risk by the parties.
Step-by-step explanation:
The doctrine of frustration is applicable to discharge a contract when an unforeseen event occurs that renders the contract physically or commercially impossible to perform, or transforms the obligation to perform into a radically different obligation from what was undertaken at the moment of entry into the contract. This doctrine is a common law principle and it applies when the event is beyond the control of the contracting parties and it was not anticipated or assumed as a risk under the contract. It must also not be the fault of either party that the event has occurred. Events that can invoke frustration include war, change in laws, death or incapacity of a person essential to the performance of the contract, or destruction of the subject matter necessary for the contract.
However, it should be noted that the doctrine of frustration is not applicable when the event should have been foreseen by the parties, when the contract makes provision for the event, or when the party seeking discharge has assumed the risk of the event occurring. Additionally, some states may not allow certain disclaimers or limitations that might otherwise exclude or limit frustration claims, and this would typically be outlined within the applicable state law.