When are banks fiduciaries of their customers and clients? This question is of more than theoretical interest given the organizational structure of modern financial institutions and the broad-ranging functions they perform. In this chapter of the Oxford Handbook of Fiduciary Law, I canvass fiduciary principles in banking law. I consider when fiduciary duties exist and what they require, the range of remedies available for breach, and the various techniques banks use to exclude or modify fiduciary duties. One puzzling feature of the legal landscape is that clients bring actions less often than banks' size and conduct might suggest, which contributes to legal uncertainty. Fiduciary law nevertheless constrains banks' activities: courts have cast banks as fiduciaries in all of the major commercial and investment banking functions, including making loans and accepting deposits, advising on merger and acquisition (M&A) transactions, and underwriting securities offerings, although banks face greater risk in some areas than others. Banks have responded by disclaiming fiduciary duties and using information barriers/Chinese walls, and yet recent judicial decisions refuse to accept these measures as automatically effective for avoiding fiduciary liability. Courts insist that they, rather than the parties themselves, determine whether fiduciary duties exist and what they require. The law thus diverges from some theoretical accounts of fiduciary doctrine, posing challenges for banks and new questions for scholars
