As a result of 2012 changes in the exemptions from registration as a commodity pool operator (CPO) available to operators of pooled investment vehicles, a large number of operators of unregistered investment companies – which may include hedge fund investment advisers, investment managers and/or boards of directors – were required to register with the Commodity Futures Trading Commission (CFTC) as CPOs, thus becoming subject to the Commodity Exchange Act (CEA) and the rules promulgated by the CFTC thereunder (CFTC Rules, and, together with the CEA, the Commodity Rules). As a result, many investment advisers that were already subject to various federal securities laws and regulations, including the Investment Company Act of 1940 (Company Act), the Securities Act of 1933, the Securities Exchange Act of 1934 and the Investment Advisers Act of 1940 and the rules under each of those Acts (collectively, Securities Rules), became subject to an additional regulatory regime. Duplicative rules and regulations are nothing new to investment advisers or CPOs, and the public, press, politicians and regulators whose collective conscience had been scarred and greatly influenced by Madoff and other scandals and a debilitating financial crisis for which many scapegoated hedge funds were not particularly concerned with creating a larger regulatory and compliance burden for investment advisers. Nevertheless, it was soon recognized that conflicting Commodity Rules and Securities Rules created an environment under which dual registrants (that is, those subject to both the Commodity Rules and Securities Rules) could not reasonably comply with certain of the conflicting requirements of both sets of rules. Rather than permit this situation to drive certain types of pooled investment vehicles either to cease or materially alter their operations due to these conflicts, the CFTC adopted rules and rule interpretations designed to resolve them (Harmonization Rules). Most of the Harmonization Rules pertain to “investment companies” registered under the Company Act (RICs), many of which are commonly referred to as mutual funds. In a guest article, Steven M. Felsenthal and Stephanie T. Green focus on those Harmonization Rules that apply to CPOs whose pooled investment vehicles are not RICs, including hedge funds and other commodity pools, describing the implications of the Harmonization Rules for such commodity pools in the process. Felsenthal is General Counsel and Chief Compliance Officer of Millburn Ridgefield Corporation, The Millburn Corporation and Millburn International, LLC; Green is a legal and compliance associate at The Millburn Corporation.