  Measuring a non-zero value for the cross section of any lepton number
violating (LNV) process would put a strong lower limit on the washout factor
for the effective lepton number density in the early universe at times close to
the electroweak phase transition and thus would lead to important constraints
on any high-scale model for the generation of the observed baryon asymmetry
based on LNV. In particular, for leptogenesis models with masses of the
right-handed neutrinos heavier than the mass scale observed at the LHC, the
implied large washout factors would lead to a violation of the
out-of-equilibrium condition and exponentially suppress the net lepton number
produced in such leptogenesis models. We thus demonstrate that the observation
of LNV processes at the LHC results in the falsification of high-scale
leptogenesis models. However, no conclusions about the viability of
leptogenesis models can be drawn from the non-observation of LNV processes.
