Static solutions of the SO(3)-symmetric Vlasov-Einstein system are studied via a variational approach. For the constitutive relation of the Emden-Fowler type phi (E, F) = Esigma +1 F-k we prove the existence of such solutions of sufficiently small mass-energy, provided 0 < <sigma> < k + 3/2. These solutions are local minimizers of the energy-Casimir functional, subjected to a variational barrier.