  A recent idea, put forward by Mund, Rehren and Schroer, is discussed; it
suggests that in gauge quantum field theory one can replace the point-localized
gauge fields by string-localized vector potentials built from gauge invariant
observables and a principle of string-independence. Based on a kinematical
model, describing unmovable (static) fields carrying opposite charges, it is
shown that these string-localized potentials cannot be used for the description
of the gauge bridges between electrically charged fields. These bridges are
needed in order to ensure the validity of Gauss' law. This observation does not
preclude the existence of Poincar\'e invariant theories, describing the
coupling of string-localized gauge invariant potentials to matter fields. But
these potentials are not a full-fledged substitute for the gauge fields in
``usual'' quantum electrodynamics.
