Illegality

What is Illegality in Contract Law?

Quick Definition

Illegality refers to situations where a contract is unlawful because its purpose, subject matter, or performance involves illegal conduct. Courts generally refuse to enforce such agreements to protect the integrity of the legal system and public interest. Depending on the circumstances, the contract may be void or simply unenforceable.

In Context

Illegality may arise where a contract involves criminal activity, fraud, tax evasion, or conduct contrary to public policy. Courts also consider whether enforcing the agreement would indirectly support unlawful behaviour. In Patel v Mirza, the Supreme Court moved away from a rigid rule-based approach and instead considered factors such as proportionality, public policy, and the seriousness of the illegality before deciding whether a claim should succeed. This modern approach gives courts greater flexibility but also requires careful balancing of competing interests. In exams, the key issue is identifying the link between the contract and the unlawful conduct, and whether public policy justifies denying enforcement.

See Also

• Legality of Object

• Public Policy

• Void Contracts

Learn More

Explore our Contract Law Notes for clearer case analysis, exam-ready frameworks, and practical guidance on handling illegality issues confidently in problem questions.