  RXTE, GINGA, and OSSE observations have revealed an intense low-energy
gamma-ray continuum emission from the Galactic plane, which is commonly
interpreted as evidence for the possible existence of a strong flux of
low-energy cosmic ray electrons. In this paper I discuss the scenario of a
hadronic origin of the soft Galactic gamma-ray continuum through inverse
bremsstrahlung. A flux of low-energy cosmic rays strong enough to produce the
observed spectrum of gamma-rays implies substantial gamma-ray emission at a few
MeV through nuclear de-excitation. It is shown that the existing limits on
excess 3-7 MeV emission from the Galactic plane, in concert with the
constraints from pion-decay gamma-ray emission at higher energies, are in
serious conflict with an inverse bremsstrahlung origin of the Galactic soft
gamma-ray emission for any physically plausible low-energy cosmic ray spectrum.
While in case of energetic heavy nuclei the limits are violated by about an
order of magnitude, for a large population of low-energy protons the implied
gamma-ray line flux and pion-decay continuum intensity are larger than the
existing limits by at least a factor of 2.
