  The (electromagnetic or weak) current operator responsible for deep inelastic
scattering (DIS) should be local and satisfy the well-known commutation
relations with the representation operators of the Poincare group. The problem
whether these conditions are compatible with the factorization theorem and
operator product expansion is investigated in detail. We argue that the current
operator contains a nontrivial nonperturbative part which contributes to DIS
even in the Bjorken limit. Nevertheless there exists a possibility that many
results of the standard theory remain.
