An action in conversion can be defeated if the right to treat the action has been waived by the plaintiff. The circumstances of a particular case may also be such as to prevent the plaintiff from holding the defendant liable for a conversion under principles of estoppel. In Addie v. Kjaer, 2009 U.S. Dist. LEXIS 15206 (D.V.I. 2009), the court stated that there can be no conversion where an owner either expressly or impliedly assents to or ratifies the taking, use or disposition of his property. A defendant may rely on the consent of the person entitled to immediate possession or that of one who has power to consent for him/her or by implication from the terms of the transaction. Consent is ordinarily a question of fact for a jury to decide.
Here in this case, the court also stated that waiver is an affirmative defense to conversion. The elements of waiver are: (1) an existing right, benefit, or advantage; (2) knowledge, actual or constructive, of its existence; and (3) actual intent to relinquish the right, which can be inferred from conduct. Generally, a waiver is a question of fact turning on the question of intent.
In Baber v. First Republic Group, L.L.C., 2008 U.S. Dist. LEXIS 45180 (N.D. Iowa June 6, 2008), the court found that ratification appears to be an affirmative defense to a conversion claim. Ratification was held to be a complete defense to a claim of conversion based on unauthorized commodities trading.