Impracticability is similar in some respects to the doctrine of impossibility because it is triggered by the occurrence of a condition which prevents one party from fulfilling the contract.
Typically, the test U.S. courts use for impracticability is as follows (with a few variations among different jurisdictions):[1] Section 261 of the Restatement (Second) of Contracts does not explicitly define the scope of what is considered impracticable, as it is a fairly subjective and fact-intensive test for the courts.
Section 2-615 of the Uniform Commercial Code deals with impracticability in the context of sales of goods, and introduces some additional constraints on the parties.
It further explains that a change in market conditions resulting in a rise or drop in prices is not sufficient to claim impracticability because the parties assumed that risk when the contract was made.
The comments indicate that contingencies such as war, embargo, crop failures, or a failure of a major source of supply that causes the market change or prevents a seller from obtaining supplies necessary for his performance would justify a claim of impracticability.