  We discuss a class of theories for Majorana neutrinos where the total lepton
number is a local gauge symmetry. These theories predict a dark matter
candidate from anomaly cancellation. We discuss the properties of the dark
matter candidate and using the cosmological bounds, we obtain the upper bound
on the lepton number symmetry breaking scale. The dark matter candidate has
unique annihilation channels due to the fact that the theory predicts a light
pseudo-Goldstone boson, the Majoron, and one can obtain the correct relic
density in a large fraction of the parameter space. In this context, the seesaw
scale is below the ${\cal{O}}(10^2)$TeV scale and one can hope to test the
origin of neutrino masses at current or future colliders. We discuss the lepton
number violating Higgs decays and the possibility to observe lepton number
violation at the Large Hadron Collider.
