  We prove a low-energy theorem valid for any model of weak scale softly broken
supersymmetry. It claims that the neutrino Majorana mass, the B-L violating
mass of the sneutrino and the neutrinoless double beta decay amplitude are
intimately related to each other such that if one of them is non-zero the other
two are also non-zero and, vice versa, if one of them vanishes the other two
vanish as well. The theorem is a consequence of the underlying supersymmetry
and independent of the mechanisms of neutrinoless double beta decay and
(s-)neutrino mass generation.
