Okla. Stat. tit. 24, § 122

Unless displaced by the provisions of the Uniform Fraudulent Transfer Act, the principles of law and equity, including the law merchant and the law relating to principal and agent, estoppel, laches, fraud, misrepresentation, duress, coercion, mistake, insolvency, or other validating or invalidating cause, supplement the provisions of the Uniform Fraudulent Transfer Act.