In many extreme emergency cases such as forest fires or tube terrorist attacks, the rescuers have difficulty using traditional legacy networks due to destruction or collapse of the infrastructure in such events. We use the term emergency mobile ad hoc networks (eMANETs) in order to describe next generation networks (NGNs) which are deployed in emergency cases. The security of these networks is critical. Especially secure routing is important given the fact that potential attackers aim to disrupt the appropriate operation of the routing protocol within an eMANET. In this paper we propose a game theoretic approach called AODV-GT (AODV-game theoretic) and we integrate this into the reactive ad hoc on-demand distance vector (AODV) routing protocol to provide defense against blackhole attacks. AODV-GT is based on the concept of non-cooperative game theory. AODV-GT outperforms AODV in terms of malicious dropped packets when blackhole nodes exist within the eMANET. Our simulations were implemented using the network simulator NS-2.