The U.N. Charter establishes that regional arrangements may not take enforcement actions without authorization from the Security Council. Yet the international community does not always enforce this Charter rule. Major international actors repeatedly tolerate deviations from it even as they assert that it allows no exceptions. This Article examines that practice, arguing that two different legal systems govern enforcement actions taken by regional arrangements. One system is reflected in the Charter text and publicly endorsed by major international actors. The second, more nebulous system is based on expectations and demands in the absence of Security Council authorization. Under this second system (here referred to as the operational system), the international community may discreetly tolerate a deviation from the Charter rule depending on the substantive interests at stake, the circumstances surrounding the lack of authorization, and the characteristics of the acting regional arrangement. In the event of a tolerated deviation, however, no actor acknowledges that it is participating in or tolerating a deviation. Instead, international actors resort to a variety of techniques to maintain the integrity of the Charter rule and to suppress acknowledgement of the operational system. After demonstrating that the Charter system and the operational system coexist in this area, this Article examines the general parameters of the operational system. It concludes that, so long as the Security Council remains ineffective in satisfying the international community’s substantive legal interests, the operational system will—and should—continue to coexist with the Charter system. The application of law in this area, therefore, cannot be fully understood without an appreciation for the role and parameters of the operational system.