  We establish the existence of spin-statistic selection rules (SSSR) for
multi-equal-photon transitions in atomic systems. These selection rules are
similar to those for systems of many equivalent electrons in atomic theory. The
latter ones are the direct consequence of Pauli exclusion principle. In this
sense the SSSR play the role of the exclusion principle for photons: they
forbid some particular states for the photon systems. We established several
SSSR for few-photon systems. 1) First rule (SSSR-1): two-equivalent photons
involved in any atomic transition can have only even values of the total
angular momentum J. This selection rule is an extension of the Landau-Yang
theorem to the photons involved in atomic transitions. 2) second rule (SSSR-2):
three equivalent dipole photons involved in any atomic transition can have only
odd values of the total angular momentum J=1,3. 3) third rule (SSSR-3): four
equivalent dipole photons involved in any atomic transition can have only even
values of the total angular momentum J=0,2,4. We also suggest a method for a
possible experimental test of these SSSR by means of laser experiments.
