Controlling the number of preemptions in realtime systems is highly desirable in order to achieve an efficient system design in multiple contexts. For example, the delays due to context switches account for high preemption overheads which detrimentally impact the system schedulability. Preemption control can also be potentially used for the efficient control of critical section behaviors in multi-threaded applications. At the same time, modern processor architectures provide for the ability to selectively choose operating frequencies, primarily targeting energy efficiency as well as system performance. In this paper, we propose the use of CPUFrequency Scaling for controlling the preemptive behavior of real-time tasks. We present a framework for selectively eliminating preemptions, that does not require modifications to the task attributes or to the underlying scheduler. We evaluate the proposed approach by four different heuristics through extensive simulation studies.