  We provide a general framework of utilizing the no-signaling principle in
derivation of the guessing probability in the minimum-error quantum state
discrimination. We show that, remarkably, the guessing probability can be
determined by the no-signaling principle. This is shown by proving that in the
semidefinite programming for the discrimination, the optimality condition
corresponds to the constraint that quantum theory cannot be used for a
superluminal communication. Finally, a general bound to the guessing
probability is presented in a closed form.
