Restatement Third of Restitution § 32
A person who renders performance under an agreement that is illegal or otherwise unenforceable for reasons of public policy may obtain restitution from the recipient in accordance with the following rules:
- Restitution will be allowed, whether or not necessary to prevent unjust enrichment, if restitution is required by the policy of the underlying prohibition.
- Restitution will also be allowed, as necessary to prevent unjust enrichment, if the allowance of restitution will not defeat or frustrate the policy of the underlying prohibition. There is no unjust enrichment if the claimant receives the counterperformance specified by the parties' unenforceable agreement.
- Restitution will be denied, notwithstanding the enrichment of the defendant at the claimant's expense, if a claim under subsection (2) is foreclosed by the claimant's inequitable conduct ([R3R § 63]).