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 Oregon, contracts made for illegal purposes or against public policy are void and unenforceable. This aligns with general contract law principles that prohibit the enforcement of agreements that involve illegal acts or that significantly contravene societal standards. On the other hand, contracts involving minors, mutual mistakes, or fraudulent misrepresentations are categorized as voidable. This means that the disadvantaged party has the option to either reject or ratify the contract. For instance, a minor in Oregon can disaffirm a contract before reaching the age of majority (18 years old) or within a reasonable time afterwards, but they also have the option to ratify the contract upon reaching adulthood. Similarly, parties to a contract based on a mutual mistake or fraudulent misrepresentation can choose to void the contract upon discovery of the issue or may ratify it by continuing with its performance. It's important to note that specific circumstances and additional rules may apply, and an attorney can provide detailed advice based on the particular facts of a case.