  We propose methods to construct gauge invariant decompositions of the nucleon
spin, particularly gauge invariant descriptions of the gluon polarization. We
show that gauge invariant decompositions of the nucleon spin can be derived
naturally from the conserved current of a generalized Lorentz transformation by
the Noether theorem. We propose a gauge invariant extension of the Chern-Simons
current as a possible description of the gluon spin, and we also examine the
problem of gauge dependence of this extended Chern-Simons current.
