imperium in imperio

Etymology
.

Noun

 * 1) A state within a state, inclusive of deep states or other forces which operate with sovereign-like impunity within a polity.
 * 2) * 1872, James Legge translating Confucius as The Ch‘un Ts‘ew, Prolegomena, Ch. iii, p. 116:
 * ...the system of presiding chiefs... was most anomalous,—an imperium in imperio,—and weakened the bond of loyal attachment to the throne. Of what use were the kings of Chow, if they could not do their proper work of government, but must be continually devolving it on one or other of their vassals?

Etymology
The expression possibly originated with Spinoza, who used it in several of his works: Tractatus Theologico-Politicus, Tractatus Politicus, and Ethica.

Noun

 * 1) imperium in imperio

Declension
As with other such expressions (e.g. ), the accompanying noun can be either singular or plural when in a plural context.