  It was recently shown that a finite imbalance between electron densities in
the $\mathbf{K}$ and $\mathbf{K}'$ valleys of bilayer graphene induces a
magnetoelectric coupling. Here we explore ramifications of this electronically
tunable magnetoelectric effect for the optical conductivity and dielectric
permittivity of this material. Our results augment current understanding of
longitudinal magnetoresistance and magnetocapacitance in unconventional
materials.
