  A rigorous light-front formalism for electron deep inelastic scattering on
unpolarized nuclei, in Bjorken limit, is reported. It preserves Poincar\'e
covariance, macroscopic locality, both number of particles and momentum sum
rules. The scheme is applied to the A=3 iso-doublet, very relevant in view of
the planned operation with unpolarized and polarized beams at the Electron-Ion
Collider. At variance with previous light-front estimates, our procedure,
including a realistic nuclear description and free-nucleon structure functions,
predicts a sizeable European Muon Collaboration effect for $^3$He. This will
allow to analyze deviations from the proposed baseline in terms of genuine QCD
effects. The extension to heavier nuclei is straightforward, although
numerically challenging.
