The only rule potentially violated would be a breach of fiduciary, owed by an agent to a principal/client. An agent cannot represent parties on both sides of a transaction (except for real estate agents, who are expressly exempt from the common law of agency under the law of every U.S. jurisdiction, including Tenn.).
The problem with the theory is that an injured party would have to show that the bank officer was impliedly acting in an agency capacity for both parties to the transaction -- or, alternatively, that the officer was acting on behalf of the adverse party while his/her conduct indicated that he/she was acting on behalf of the injured party, or only on behalf of the bank.
The law of agency provides that an agency relationship can be created expressly, via an oral or written contract
; impliedly via the actual conduct between parties (termed, "actual authority"); via a manifestation of the principal to third parties (termed, "apparent authority"), or via operation of law (termed "ostensible authority") -- such as where a parent acts to bind a minor child to a particular activity, to which the child could not bind his/herself.
Also, an agent can create a warranty of agency authority, even if no actual, apparent or ostensible authority exists, by manifesting agency authority to a third party -- and thereby the agent becomes liable for the promises made, even if the agent's principal/client never authorized the agent's actions.
Anyway, that's the broad stroke. If you want to hold the bank officer liable, you will have to show that he/she misrepresented his/her actions so as to induce your justifiable reliance, and that as a result, you suffered some sort of definite and certain injury and consequent economic damage.
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