In Rutherford’s framework, the law precedes the king, defines the office, and constrains every occupant of it. One of the central arguments in Samuel Rutherford’s Lex Rex is that monarchical authority is constitutionally bounded at every point — from who may hold the office, to how they obtain it, to what they may do once installed. These limits are not merely practical recommendations but structural requirements rooted in Scripture, natural law, and the historical practice of covenanted peoples. If monarchy were truly absolute and hereditary by divine right, none of these limits would exist. Their existence indicates that kingship is, in Rutherford’s view, a delegated trust rather than a personal possession.
The King Must Be Chosen from Among the People
Rutherford draws heavily on Deuteronomy 17:14–15, which prescribes that the king must be selected “from among thy brethren” and explicitly forbids the appointment of a stranger. This is not an incidental detail — it is a constitutional prerequisite written into the law before Israel ever had a king. The implication is twofold. First, the people possess an active role in choosing their ruler. The text does not say God will unilaterally install a king upon the nation; it says the people will set a king over themselves, within parameters God has laid down. Second, the pool of eligible rulers is limited. Not any conqueror or foreigner may assume the throne. The office is bounded by identity and relationship to the governed community.
This principle directly undermines the absolutist claim that kings rule by divine fiat irrespective of popular consent. If God Himself set qualifications on who could be king, then the office is definitionally limited. The monarch is a constitutional officer — powerful, but not sovereign in the unbounded sense royalists claimed. True sovereignty, in Rutherford’s framework, remains with God and is mediated through the law and the consent of the governed. This theological architecture is the same foundation upon which later documents like the Declaration of Independence would be built: governments derive their just powers from the consent of the governed.
Conquest Does Not Constitute Legitimate Rule
Rutherford addresses the common royalist argument that conquest establishes kingship. He flatly rejects it. A conqueror who rules without the consent of the people is not a king but a royal robber. The mere fact that someone possesses military power sufficient to seize a throne does not invest the act with moral or legal legitimacy. Power and authority are distinct categories. Authority requires lawful origin — either through election, covenant, or consent — while raw power is morally neutral at best and tyrannical at worst.
This distinction matters enormously for resistance theory. If conquest alone could create lawful kingship, then no act of resistance could ever be justified, because every successful tyrant would be, by definition, a lawful ruler. Rutherford’s rejection of conquest-as-legitimacy preserves the moral and legal space for the right of resistance. A ruler who obtained power through force and governs without consent is precisely the kind of tyrant against whom lesser magistrates and the people may take defensive action — a principle further developed in the Vindiciae Contra Tyrannos.
Primogeniture Is Not Absolute
One of the most practically significant arguments in Lex Rex concerns hereditary succession. Royalists held that the eldest son of a king held an indefeasible divine right to the throne. Rutherford demolishes this claim with Scripture’s own record. Solomon was chosen as king over his elder brother Adonijah. If strict primogeniture were God’s law, this would have been an act of injustice. Instead, it demonstrates that birth order is a factor but not a determinative one — the people’s ratification and God’s providential will must confirm any succession.
This argument carries two implications. First, succession is not automatic. Even a divinely favored individual like Solomon required formal installation through the consent of the governed. The coronation was not a ceremony acknowledging an already-existing right; it was the act that actually constituted the authority. Without the people’s confirmation, the claim remained incomplete. Second, this means the community retains a veto over unfit heirs. If the eldest son is manifestly unfit — tyrannical in character, hostile to the law, or destructive of the common good — the people are not bound to accept him simply because of the accident of birth order. The office exists for the people’s welfare, not the dynasty’s perpetuation.
The King as Constitutional Officer
Taken together, these three constraints — ethnic and communal qualification, consent rather than conquest, and conditional succession — define the king not as an absolute sovereign but as a constitutional officer bound by the terms of his appointment. The law is king (lex rex), not the king as law (rex lex). This is the inversion that gives Rutherford’s treatise its title and its revolutionary force.
A king who violates these constitutional limits — who rules as a foreigner imposed by conquest, or who seizes the throne by force without popular consent, or who inherits the crown despite manifest unfitness — is not exercising legitimate authority. He is exercising mere power, and power without lawful authority is tyranny. Against tyranny, the doctrine of lesser magistrates provides the mechanism for lawful resistance: intermediate authorities, themselves constitutionally appointed, may resist and restrain a lawless superior.
This constitutional understanding of monarchy was not merely academic. It shaped the Magna Carta’s insistence that the king was under law, the Scottish covenanting tradition’s resistance to Stuart absolutism documented in Scottish Church History and Religious Resistance, and ultimately the American founding generation’s assertion that no government may rule without the consent of the governed. The thread from Deuteronomy 17 through Rutherford through 1776 is direct and unbroken.
Relevance for the Prepared Citizen
Understanding constitutional limits on authority is not antiquarian curiosity — it is the intellectual foundation for the Sixth Commandment and the Second Amendment argument that the right and duty of self-defense exists precisely because government power is bounded and fallible. If rulers were truly absolute and divinely guaranteed to be just, there would be no need for an armed citizenry. The entire tradition of the citizen-soldier rests on the premise that authority is delegated, conditional, and accountable — and that when it fails, the people must be prepared to defend themselves and their communities. The practical implications extend from constitutional law into the jurisprudence of the Second Amendment and the daily reality of armed citizenship.