  We investigate a double-layer of penetrable ions near a charged wall. We find
a new mechanism for charge reversal that occurs in the weak-coupling regime
and, accordingly, the system is suitable for the mean-field analysis. The
penetrability is achieved by smearing-out the ionic charge inside a sphere, so
there is no need to introduce non-electrostatic forces and the system in the
low coupling limit can be described by a modified version of the
Poisson-Boltzmann equation. The predictions of the theory are compared with the
Monte Carlo simulations.
