  Relativistic Schroedinger Theory (RST), as a general gauge theory for the
description of relativistic N-particle systems, is shown to be a mathematically
consistent and physically reasonable framework for an arbitrary assemblage of
positive and negative charges. The electromagnetic plus exchange interactions
within the subset of {\it identical} particles are accounted for in a
consistent way, whereas {\it different} particles can undergo only the
electromagnetic interactions. The origin of this different interaction
mechanism for the subsets of identical and non-identical particles is traced
back to the fundamental conservation laws for charge and energy-momentum: in
order that these conservation laws can hold also for different particles, the
structure group $\mathcal U(N)$ of the fibre bundles must be reduced to its
maximal Abelian subgroup $\mathcal U(1) \times \mathcal U(1) \times ... \times
\mathcal U(1)$, which eliminates the exchange part of the bundle connection.
The persisting Abelian gauge symmetry adopts the meaning of the proper gauge
group for the electromagnetic interactions which apply to the identical and
non-identical particles in the same way. Thus in RST there is an intrinsic
dynamical foundation of the emergence of exchange effects for identical
particles, whereas the conventional theory is invaded by the exchange
phenomenon via a purely kinematical postulate, namely the antisymmetrization
postulate for the wave functions due to Pauli's exclusion principle. As a
concrete demonstration, a three-particle system is considered which consists of
a positively charged particle of arbitrary rest mass and of two negatively
charged particles of equal spin, mass and charge (e.g. electrons).
