In a radio system where wireless nodes are in contact, the wireless nodes are enabled to exchange information with adjacent nodes. In addition, in one embodiment distant nodes out of range for direct communication can be communicated with by forwarding data over multiple hops. When a user, in particular a primary user, is detected by a node, a spectrum access blocking message is sent, to other nodes in the vicinity of the node thereby enabling blocking of the radio resource in a geographical area in which the other usage is detected. This means that the radio resource is blocked in that area from being accessed by other users than the primary user. The blocking message can be distributed in any suitable manner and can be tailored for the application at hand.