We consider the decentralized power allocation and spectrum sharing problem in multi-user, multi-channel systems with strategic users. We present a mechanism/game form that has the following desirable features: 1) it is individually rational; 2) it is budget balanced at every Nash equilibrium of the game induced by the game form as well as off equilibrium; and 3) the allocation corresponding to every Nash equilibrium (NE) of the game induced by the mechanism is a Lindahl allocation, that is, a weakly Pareto optimal allocation; conversely, every Lindahl equilibrium results in a NE of the game induced by the game form. Our proposed game form/mechanism achieves all the above desirable properties without any assumption about, concavity, monotonicity, or quasi-linearity of the users' utility functions.