The concept of Quality of Service (QoS) offers different service levels to the network users. Through Service Level Specifications (SLSs), the users in a wireless network, which supports QoS, are able to express, at run-time, their expected service requirements through well defined parameters. Conventional QoS parameters, such as throughput, delay, jitter, packet loss rates, and so forth, are used for reliably ensuring a certain service level with respect to reliability and/or performance. However, most existing researches have ignored tunable security as a Quality of Service (QoS) parameter. The biggest challenge of integrating QoS and security parameters consists in their contrasting goals. This paper presents an idea to permit the users of an IEEE 802.11 Wireless Local Area Network (WLAN) to specify their security and QoS requirements in their Service Level Specifications (SLSs). Then, a game theoretic approach is presented so that the system can reach Service Level Agreement (SLA) with the users to ascertain a balanced set of security and QoS parameters for the users. The effectiveness of the proposed approach is verified through computer simulations.