Limits on the mass of the muon neutrino in the absence of muon-lepton-number conservation

We show that muon neutrinos of masses greater than 10^-2, 6, or 25 keV (depending upon the particular class of theories) may decay in less than the lifetime of the universe in wide classes of weak-interaction theories which violate separate muon-lepton-number conservation. We conclude that the astrophysical limit of Cowsik and McClelland on the mass of light neutral particles cannot be applied to the muon neutrino in the absence of experimental limits on its mass at these values.