Barb, I didn't see anything similar in Mich. state law (but I didn't do exhaustive research, either.) Rather, I'd say it's a matter of contract. Here's a section of our deposit account agreement:
AUTHORITY. You will not grant anyone authority to conduct business with us on your behalf until we have reviewed the terms of authorization and have given you written acceptance. This includes authority such as power of attorney, bill-paying arrangement, or other method. You will not claim that we wrongfully dishonored items presented to us before we accepted the authorization. If you have not given us the proposed authorization for advance review, we may, in good faith, honor items and instructions from the person you authorized. You will not hold us responsible if someone you authorized to do business with us misapplies your money. You assume all risk of improper acts by such person. We can consider an authorization valid until we actually receive written revocation of it and have had reasonable time to review and act upon it. If we accept an authority, we may revoke our acceptance of that authority at any time at our discretion.
(We use Bankway forms from Kirchman.)
I think this covers us - from the CIP perspective, Tom is providing good advice. Make sure the POA is who they say they are. In the circumstances you describe, there will always be some risk.
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Opinions are Bartman's, not those of my employer. "A noble spirit embiggens the smallest man."