This paper presents the policy and technology case for decentralizing the architecture for dynamic spectrum management. A specific system concept called SMAP (distributed spectrum management architecture and protocol) is intended to enable wireless devices and networks to coordinate their spectrum use through an Internet-based common spectrum control plane. The SMAP architecture supports peer exchange of radio usage and control parameters between multiple wireless network domains operating in the same geographic region so that they can run distributed algorithms for optimization of transmission parameters to achieve efficiency and fairness while adhering to global and local policies. The architecture also provides interfaces to higher level cloud services including spectrum aggregators which facilitate broader cooperation and business relationships between wireless domains in the same area, or to regional spectrum databases such as the SAS (spectrum access system) being used for the 3.5 GHz innovation band. Design requirements for the proposed distributed spectrum control plane are discussed, including efficiency, scalability, decentralized decision making, support for local policy, service-level agreements and market mechanisms. This is followed by a technology outline of the architecture, explaining the high-level organization of the spectrum control plane, the participating entities, their protocol syntax and types of spectrum algorithms supported. Support for local policy and spectrum markets is also discussed. Proof-of-concept simulation and/or experimental results which demonstrate the technical feasibility of the proposed techniques are given for the following scenarios: (1) logically centralized spectrum coordination via regional spectrum brokers; (2) distributed coordination between colocated wireless domains using either single or multiple radio technologies (such as Wi-Fi and LTE); and (3) distributed coordination with additional local policy constraints. Future work is discussed in conclusion.