A more thorough explanation:

An implied-in-law condition is a future and uncertain event on which the existence or extent of an obligation or liability depends. It is a condition that is not expressly mentioned but is imputed by law from the nature of the transaction or the conduct of the parties to have been tacitly understood between them as a part of the agreement.

For example, if Jones promises to pay Smith $500 for repairing a car, Smith's failure to repair the car (an implied or constructive condition) relieves Jones of the promise to pay. This means that if Smith does not repair the car, Jones is not obligated to pay him the $500.

Another example of an implied-in-law condition is the cooperation of the parties to a contract. It is understood that both parties must cooperate to fulfill their obligations under the contract, even if it is not expressly stated in the agreement.