Comparing Frustration of Contract in Common Law with Force Majeure, Rule of Hardship and Hardship

The binding force of contract as one of the important principles of contract law is accepted in all legal systems of the world, whereby the two parties are obliged to implement their contractual commitments, However, sometimes circumstances arise that make it impossible to execute the contract or cause substantial changes in the conditions of the contract so that the performance of contractual obligations becomes difficult. These events are studied under the subject of the legal excuses of the implementation of the contract. Of the main theories of legal excuses, the doctrine of frustration of contract in common law, the rule of hardship in Islam, force majeure and hardship in the principles of international commercial contracts (UNIDROIT Principles) are at issue. The opinions expressed in this regard are very similar to each other from the point that the exemption of obligator from his commitment and the dissolution of the contract may be a result of an external event which makes the performance of the contract impossible or significantly difficult. Based on similarities between these theories in this article, this study attempts to examine the similarities and differences of these opinions