My textbook (Halliday & Walker) explains that a charged conductor (a solid, of an arbitrary shape) in electrostatic equilibrium will have the electric field inside be 0 and all electrons will be on its surface. It proves this by saying that if the electric field inside was not 0, the free electrons would move and cause a current, and by our equilibrium assumption no such current exists. Then it applies Gauss's law, with an imaginary closed surface S anywhere inside the conductor. Since E inside is 0, flux through S will be 0 too, and so the net charge inside is 0. Therefore, no free electrons will be inside, rather they will all be on the surface. That's fine, but can't we just as easily apply the same reasoning to these electrons on the surface as well?! Just draw a closed surface S1 around those electrons, but still (infinitesimally) within the conductor. Since those electrons are not moving, the field inside S1 must be 0. And so the flux is too, and so the net charge inside is 0. But we know that S1 encloses a net charge - all those electrons on the surface of the conductor! Seems like a contradiction. Where is the flaw in this reasoning?