  The Global Color-symmetry Model of QCD is extended to deal with a background
electromagnetic field and the associated conserved current is identified for
composite $\bar{q}q$ pion modes of the model. Although the analysis is limited
to tree level in the bilocal fields that bosonize the model, the identified
photon-pion vertex produces the charge form factor associated with ladder
Bethe-Salpeter pion amplitudes. A Ward-Takahashi identity for this vertex is
derived in terms of the effective inverse propagator for the equivalent local
pion field and the intrinsic ladder Bethe-Salpeter amplitudes. This identity is
then used to illustrate gauge invariance by showing that identical vertex
information is produced from the gauge change of the free action once proper
account is taken of the gauge transformation properties of the bilocal pion
fields. Comments are made on the location of the vector dominance mechanism in
this treatment.
