On the charge invariance and relativistic electric fields from a steady conduction current

It is shown that a modified form of charge invariance, as proposed in the literature recently, is only a special case of the standard principle of charge invariance. Moreover the thereby inferred presence of second-order electric fields outside a steady conduction current is actually the result of an independent second assumption of the unequal number densities of positive and negative charges, which has no theoretical or experimental support.