Banker Loyalty in Mergers and Acquisitions

76 Pages Posted: 23 Sep 2015 Last revised: 1 Oct 2016

See all articles by Andrew F. Tuch

Andrew F. Tuch

Washington University in St Louis - School of Law; European Corporate Governance Institute (ECGI)

Date Written: September 21, 2015


When investment banks advise on merger and acquisition (M&A) transactions, are they fiduciaries of their clients, gatekeepers for investors, or simply arm’s-length counterparties with no other-regarding duties? Scholars have generally treated M&A advisors as arm’s-length counterparties, putting faith in the power of contract law and market constraints to discipline errant bank behavior. This Article counters that view, arguing that investment banks are rightly characterized as fiduciaries of their M&A clients and thus required to loyally serve client interests.

This Article also develops an analytical framework for assessing the liability rules that will most effectively deter disloyalty on the part of investment banks toward their M&A clients. Applying optimal deterrence theory, the framework shows why holding only banks liable for disloyalty is unlikely to effectively deter such disloyalty. Instead, it suggests the need for fault-based liability rules to be applied to corporate directors (of M&A clients) for their oversight of the banks they engage as well as the potential need for public enforcement of certain hard-to-detect conflicts.

Applying this framework, this Article assesses existing law, focusing on recent Delaware decisions, generally supporting that law but arguing that it is unlikely to effectively deter advisor disloyalty. It suggests changes to address the regulatory gap.

Keywords: Mergers and acquisitions, investment banking, financial advisors, fiduciary duties, engagement letters, optimal deterrence, aiding and abetting liability, Del Monte, El Paso, RBC Capital

JEL Classification: K10, K22, G20, G21, G24, G34

Suggested Citation

Tuch, Andrew F., Banker Loyalty in Mergers and Acquisitions (September 21, 2015). 94 Texas Law Review 1079 (2016), Washington University in St. Louis Legal Studies Research Paper No. 15-09-10, Available at SSRN:

Andrew F. Tuch (Contact Author)

Washington University in St Louis - School of Law ( email )

One Brookings Drive
Saint Louis, MO 63130
United States

European Corporate Governance Institute (ECGI) ( email )

c/o the Royal Academies of Belgium
Rue Ducale 1 Hertogsstraat
1000 Brussels

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