An attempted contract that is made for an illegal purpose or that is against public policy cannot be enforced by either party and is void. In contrast, a contract that is made by a minor (usually under age 18), or that is based on a mutual mistake, or that was made on the basis of a fraudulent misrepresentation by one party, is voidable and may be rejected by a party who was at a disadvantage when the contract was made. A voidable contract may also be ratified and accepted by such a party—after a child reaches the age of majority (usually 18), or the parties become aware of their mutual mistake, or a party learns of the other party’s misrepresentation and proceeds with performance of the contract.

In California, contracts made for illegal purposes or against public policy are considered void and unenforceable. This means that if the subject matter of the contract is illegal, such as a contract for the sale of prohibited substances, or if it violates established public policy, neither party can seek legal recourse to enforce the terms of the contract. On the other hand, contracts that are voidable can be enforced or rejected at the discretion of the disadvantaged party. This includes contracts entered into by minors (under the age of 18), contracts based on mutual mistakes, or contracts formed under fraudulent misrepresentation. A minor has the right to disaffirm a contract before reaching the age of majority and for a reasonable time after, but they may also choose to ratify the contract upon reaching adulthood. Similarly, parties to a contract can either rescind or ratify the agreement once a mutual mistake or fraud is discovered. It's important to note that specific rules may apply to the ratification or disaffirmance of contracts, and an attorney can provide guidance on the legal options available in such situations.