One of the key legal foundations for certain rescission rights (khiyarat) in civil law is the concept of a \\\\\\\\\\\\\\\"defect of will.\\\\\\\\\\\\\\\" This theory posits that rescission rights are a mechanism to remedy deficiencies in the consent (rida) of contracting parties. Specifically, it argues that in cases such as khiyar al-‘ayb (rescission due to latent defects) and khiyar al-ghabn (rescission due to gross inequity in the price), the aggrieved party\\\\\\\\\\\\\\\'s consent is vitiated by an underlying defect. Proponents of the defect of will theory highlight principles such as the qawaid al-iqdam (principle of voluntary risk assumption), the rational foundation of rescission rights, the waiver of rights through conduct, waiver clauses within contracts, and the concept of mitigating harm as supporting evidence. They assert that this theory provides a more comprehensive and coherent explanation of the rules governing rescission rights compared to the la darar (no harm) rule, and it aligns more closely with established civil law and Islamic jurisprudence. In Afghanistan, the Civil Code explicitly recognizes the defect of will as the basis for rescission rights. Concepts like ghabn (unfair advantage) and tadlis (fraudulent misrepresentation) are considered defects in consent under Afghan law. In Iranian civil law, some scholars also refer to the defect of will as a basis for certain rescission rights. While several of these rescission rights clearly stem from a defect in consent, the drafters of Iran\\\\\\\\\\\\\\\'s Civil Code, following Islamic legal traditions, have categorized these rights as grounds for contract termination (rescission) rather than treating them as cases of contract invalidity arising from defective consent (as stipulated in Article 199). This approach does not negate the la darar principle but acknowledges its limitations in fully explaining the legal scope of rescission rights. The defect of will theory, on the other hand, offers a more precise and well-grounded framework for interpreting the rules of rescission and exhibits greater congruence with both civil law doctrine and Islamic jurisprudence. Consequently, it provides a more comprehensive foundation for justifying rescission rights in both jurisdictions.

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