The Dodd-Frank Act, in section 619 defines Volcker. https://docs.google.com/open?id=0B_7ryVB5lSIoZjU4ODJmNjAtOTczNi00NTFhLWI4ZTktYzY0ZjZmMGFkOTQ1

How this differs from the 300+ pp Rule Text is that the Rule Text is the implementation, written by Regulators, of section 619 in Dodd-Frank.