  The Standard Model is extended minimally with a new flavor-violating family
symmetry ${\rm U(1)}_\lambda$, which acts only on leptons including the
right-handed neutrinos. The model is anomaly free with family-dependent ${\rm
U(1)}_\lambda$ charges, and consistent with the observed neutrino mixing
angles. It predicts charged lepton flavor-violating processes mediated by a new
gauge boson. Under certain conditions, the smallness of $\theta_{13}$ of
neutrino mixing can be justified in terms of the muon-to-tau mass ratio, at the
same time explaining the electron-to-tau large mass hierarchy.
