  The stability of proton and neutrino masses are discussed in the
Randall-Sundrum model. We show that relevant operators should be suppressed, if
the hierarchical Yukawa matrices are explained only by configurations of
wavefunctions for fermions and the Higgs field along the extra dimension. We
assume a $Z_N$ discrete gauge symmetry to suppress those operators. In the
Dirac neutrino case, there is an infinite number of symmetries which may forbid
the dangerous operators. In the Majorana neutrino case, the discrete gauge
symmetries should originate from $U(1)_X$ gauge symmetries which are broken on
the Planck brane. We also comment on the $n-\bar{n}$ oscillation as a
phenomenon which can distinguish those discrete gauge symmetries.
