In recent years,“separation of banking and commerce”,“separation of banking and media”, and“separation among banking institutions”are all recurring keywords when referring to financial regulation in Taiwan. However, matching concepts in comparative banking law, even imperfect ones, are less often discussed. Using the notions and legal rules developed in the United States as the benchmarks, this Article examines and analyzes these related concepts—in form or of function—and their uses in the United States.The general“firewall”policy in American banking law has gone through several stages, including branch restriction, related-party transaction regulation, separation of commercial and investment banking, breakdown of the Glass-Steagall Wall, and the re-introduction of Volcker Rule by the Dodd-Frank Act as a keystone in mending the fallout of 2008 financial crisis. On the surface, these changes evolve and converge toward the structural design of any financial holding company. However, this organizational form has created unexpected challenges to modern financial regulation, including lack of transparency, obscuring the role as an intermediary and trading opponent, over-complex product design, and excessive size of financial conglomerates, which causes wealth concentration, political unease, as well as“too big to fail”when happened. This is exactly the background of the returning of Volcker Rule in 2010.However, Taiwan not only faces a similar structural threat brought by financial holding companies as what is in the U.S., but also encounters its local idiosyncrasy when crafting its version of“separation policy.”To respond to this intricate nature of this issue, this Article investigates the historical developments in the banking law in the United States. The hope is that these experiences would serve as a useful reference for Taiwan’s handling of this myriad of concepts.