  We consider a non-uniqueness problem of gauge invariant nucleon spin
decomposition. A gauge invariant decomposition with a generalized Coulomb
constraint for the physical gluon has been constructed. The decomposition
scheme is consistent with the concept of helicity in non-Abelian gauge theory.
We provide an explicit representation for the gauge invariant Abelian
projection which implies further separation of gluon into binding and valence
parts.
