In this paper, a theoretical investigation of the locking of two weakly coupled semiconductor lasers is presented. The analysis begins with a set of rate equations for the electric fields and carrier densities inside each laser diode cavity. From these, the dynamic stability of the solutions as a function of the detuning between the lasers and the linewidth enhancement factor of each laser is determined. It is seen that when the linewidth enhancement factor is the same for both lasers, the entire locking bandwidth is dynamically stable. When the linewidth enhancement factor is different for the two lasers, asymmetric locking occurs, and only a portion of the locking bandwidth is dynamically stable.