In this paper, we propose a decentralized supervisory control approach for distributed adaptive systems. The adaptive systems are modeled, through their adaptation managers, as synchronous reactive systems using finite state machines with inputs/outputs and transition guards. When system complexity increases, critical properties cannot be verified intuitively. Therefore, formal and automated control synthesis methods are needed, for supervising the way the adaptation managers are coupled with the system, and for ensuring additional safety properties. We propose the adaptation of existing techniques for discrete controller synthesis, to control decentralized systems that are composed of several subsystems spread across remote sites. Our approach consists of computing, for each site, abstracted behavior models for each distant subsystem. These behavior models will be coupled with the considered local subsystem, in order to compensate for the lack of information caused by the distribution constraints. Then we apply discrete controller synthesis on each site to obtain local controllers. These controllers, acting on their corresponding subsystems, will ensure that the global behavior property is respected.