Rule of Law implies minimising the arbitrary exercise of powers by the government and bringing the state under the purview of a set of well established laws where justice is equal for all sections of people.
Suppose, in a given society murder is prohibited by the government according to law. But at the same time, refuses to arrest or prosecute a high ranking authority who intentionally kills an innocent person without any valid reason. His position is given due respect not the law. This implies sheer violation of the Rule of Law where justice must be equal for one and all.