  Background: Phenomenological Poincar\'e invariant quantum mechanical models
can provide an efficient description of the dynamics of strongly interacting
particles that is consistent with spectral and scattering observables. These
models are representation dependent and in order to apply them to reactions
with electromagnetic probes it is necessary to have a consistent
electromagnetic current operator.
  Purpose: The purpose of this work is to use local gauge invariance to
construct consistent strong current operators.
  Method: Current operators are constructed from a model Hamiltonian by
replacing momentum operators in the Weyl representation by gauge covariant
derivatives.
  Results: The construction provides a systematic method to construct explicit
expressions for current operators that are consistent with relativistic models
of strong interaction dynamics.
