  Following a previous proposal, lepton number is considered as the result of a
spontaneously broken non-Abelian gauge $SU(2)_N$ symmetry. New fermions are
added to support this new symmetry, the spontaneous breaking of which allows
these new fermions to be part of the dark sector, together with the vector
gauge boson which communicates between them and the usual leptons. A byproduct
is a potential significant contribution to the muon anomalous magnetic moment.
