A method and system for controlling access to a spectrum resource by radio devices that are grouped into a first class and a second class, the first class having higher priority to the spectrum resource than the second class. The control techniques include setting a weight for each radio device in each class of radio devices; setting a threshold for each class of radio devices; aggregating the weights of radio devices that use the spectrum resource; and determining if the aggregate weight crosses the threshold for one of the classes of radio devices and, if so, denying access to the spectrum resource for additional radio devices belonging to the class of radio devices associated with the crossed threshold.