This post consists of excerpts from two sources. Thomas Aquinas is the most influential theologian since Agustine and prior to the Protestant Reformation.

An excerpt from ‘DEATH TO TYRANTS’: THE POLITICAL PHILOSOPHY OF TYRANNICIDE – PART I
By SHANNON K. BRINCAT
Available here: https://docs.wixstatic.com/ugd/056e76_68f6ed552ce547569217910d94080a85.pdf

Aquinas offered a limited acceptance of tyrannicide which perhaps unintentionally contradicted Augustine’s work. Overall, Aquinas finds in favour of tyrannicide where the positive law of the tyrant opposed the principles of justice in relation to natural law, a tradition begun by Cicero. For Aquinas, tyranny is the most unjust form of government because it is directed to the personal interest of the ruler who oppresses by might instead of ruling by justice, and who seeks his own aggrandisement rather than the good of the multitude subject to him (1969: 178, 181). For him, ‘the princes of the earth’ are instituted by God not that they may seek their own profit but in order to ensure the common well-being and it is on the basis of this belief that Aquinas constructs a system of guarantees to save the state from governments that are opposed to natural law (1935: Lib. I, c.6). For Aquinas mutual love is commanded by divine law which requires the necessary formation of a civil community that is ‘united with regard to that which is common’ (1935: Lib. I, c.1). This notion of the common good holds that any arbitrary intervention on the part of the ruler that would be destructive of individual good and liberty would be contrary to this provision and the ‘eternal law’ which governs the rulers themselves (Aquinas1985a: Ia IIae q 96, Article 3). This analysis is then extended in Sentences where Aquinas develops his argument that ‘Christians are not held to obey secular powers, and especially tyrants’ because they have been made the sons of God and are therefore ‘free everywhere’. Through a series of objections and counters Aquinas concludes that like the Holy Martyrs who ‘suffered death rather than obey the impious orders of tyrants’, ‘when there is no recourse to a superior by whom judgment can be made . . . then he who slays a tyrant to liberate his fatherland is praised and receives a reward’ (1985b: Distinction 44, Question 2,Article 1). Similar to the conception of freedom under Roman law, Aquinas likens the state of tyranny to slavery (1985a: Vol. 41) and claims that there is no difference between being subject to a tyrant and being ravaged by a wild beast (1988: 20).

For Aquinas, the mere will of the ruler does not necessarily have the force of law as in accordance with the Gelasian concept of the twin authorities(spiritual and temporal); the positive civil law of the state (ius civile) is inferior and subordinate to natural law and the morals of society (ius naturale). Over the spiritual order, temporal authority hasab initiono jurisdiction. If, at any point, positive law defects from the law of nature it becomes a perversion which a citizen may legitimately refuse to obey (1985a: Ia IIae, Question 95,Article 2). Moreover, the ruler is vice gerens of the people and does not have the power to frame laws except as representing their wishes (1985a: Ia IIae,Question 97, Article 3). Tyranny therefore exceeds its secular authority and the tyrant forfeits the loyalty of the community having not ruled for the common good as the office requires. For Aquinas the tyrant by usurpation is not a true authority and a tyrannical law has the character of an act of violence that appears legally authoritative only because it is a dictate of a superior over his subjects(1948: 633). Quoting Augustine favourably, Aquinas finds that an unjust law ‘is considered to be no law at all’ and does ‘not bind in conscience’ (1988:53–5). In effect, the commands of the tyrant cease to be law as they do not accord to natural law or the common good and may be legitimately disobeyed. For Aquinas, subjects have no duty to obey laws under any regime marked by injustice or usurpation, and it is during such times where the state is the ‘egoime of a band of brigands’, that he is permissible of tyrannicide (1988: 71–3).While Aquinas strongly favoured non-violent means of resistance to tyranny and counseled prudent toleration in cases of ‘mild tyranny’, in conditions where the tyranny is extreme he justifies tyrannicide as necessary for the welfare of the whole community ‘for a little leaven sours the whole lump’ (1985a: Vol.38, 23). Based on certain Biblical passages such as Ehud’s killing of Eglon, and Moses’ murder of the Egyptian slaver, he claims that ‘it is praiseworthy to deliver a multitude from tyrannical rule’ (1985a: Part II, Object 3, Question 42). Aquinas emphasises that where the “‘good” stand to gain security, the wicked may be legitimately killed’ and at such times the overthrow of tyranny does not have the character of sedition. Rather, it is the tyrant that is guilty of sedition since he encourages discord among his subjects (1988: 65 and 103 ff.). This is the basis of Aquinas’ restrictive view of the legitimacy of tyrannicide (Gilby 1958).However, extending Aristotle’s doctrine of meloir pars, Aquinas recommends that opposition to tyranny be entrusted to those institutional bodies that have the right to do so, rather than the individual (1985a: Question 97). The problem with this last criterion however, is that it fails to anticipate that under tyranny such bodies are likely to have already been subsumed under the tyrant’s control and therefore rendered incapable of resistance.

Moving on into Counter-Reformation literature, Suarez and Mariana shared Aquinas’s view regarding the permissibility of tyrannicide. Their important contribution was to base their conclusion on the ‘derived authority’ of the legitimate ruler which they claimed emanates from the people rather than natural law. This socio-political argument concerning the relationship between citizen and ruler informs those of the later liberal philosophers. Suarez argued that the civil ruler obtains authority from the consent of the community by their ‘special volition’ to form one political body (1944: Vol. II). The power of the sovereign to make laws is that transferred to him by the community and the ruler acts in a corporate capacity to this end (Skinner 1978: Chapter 5). This power is held in common and does not reside in any specific individual but in the community as a whole, and cannot therefore be deferred to any one prince – or tyrant. Consequently, Suarez found violence readily permissible against the usurper as the community had not consented to his rule and was not obligated to him and yet he remained far more reticent regarding violence against the tyrant in regimine(1944: Vol. II).

Mariana shared Suarez’s general argument that in the advent of tyranny the people may revoke the ruler’s authority, depose, and in certain circumstances kill him. Both writers validated the right of resistance on the grounds that political power is invested in the people and is delegated, not inherent, in the ruler (Mariana 1948). However, Mariana bypassed the distinction between tyranny by usurpation and conduct, arguing for every individual’s right to kill tyrants with certain restrictions. As with Aquinas, Mariana believed that the people ought to bear with a tyrant as long as possible and to take violent action only when tyrannical oppression had surpassed all bounds. Similarly, he agreed that tyrannicide was valid only where public judgment could not be given and insisted that tyrannicide be public rather than conspiratorial in method. Importantly, Mariana stipulated that an integral factor in assessing the just nature of tyrannicide was the probable improvement in civilian life after the removal of the tyrant, citing with approval the convalescence in Roman life after the tyrannicide of Caracella (207 AD) and of Domitian (96 AD) (Connell1970). Following similar reasoning to Aquinas, Mariana asserted that there is no sedition in tyrannicide unless the polity is disturbed so inordinately that citizens suffer greater harm from the consequent disturbance than from the tyrant’s oppression. If these requirements are satisfied, then Mariana claims that proportional force as used by the tyrant in assuming power is legitimate against them (Mariana 1948).

In distinction to the permissive view of these Jesuit thinkers who purposefully depreciated the royal while exalting the papal prerogative, Reformation philosophy on tyrannicide is divided between the submissive doctrines of the Gallicans and Anglicans, and the nascent Republicanism of the Puritanist branch. For the French Gallicans the advent of tyranny could not release the nation from the dutiful obligation of obedience – the popular notion held that if the rulers are as wolves, the Christians must show themselves as sheep (Lecky 1913: Chapter 5). Similarly, Anglican doctrine avowed complete submission to whosever ruled the state, leading to Taylor’s expressed resignation to tyranny: ‘let the powers set over us be what they will, we must suffer it and never right ourselves’ (Lecky 1913: 2). Yet, whereas Gallican and Anglican doctrine advocated submission to tyranny there was an equal tendency within Reformation thought which contained a political predisposition to Republicanism and argued for the permissibility of resistance to tyranny(Calvin 1954: Book IV, Chapter XX). For example, von Hutten interpreted Reformational tenets mainly as principles of liberty, emancipating men from both intellectual and political tyranny (Lecky 1913: 164). Similarly, Puritanism advocated the principle of popular election and, based on Biblical authority, held the reform of the world as their Christian duty. This included the right to openly defy established laws and with armed force to accomplish what they believed was right, which could have included tyrannicide (Berman 1983: 31 ff.). Such ideas were to resound strongly within liberal theory regarding tyrannicide.

Though Luther and Calvin shared the belief that to rebel was to dispute against the order instated by God (Luther 1983: Vol. 44, 45) both writers may be interpreted as permitting tyrannicide in certain circumstances (Luther 1983:Vol. 46; Vol. 45: 113). Luther held that only the whole community could condemn the tyrant to death (Waring 1968: 14–16) but Calvinist principles provided for a ‘duty of resistance to tyrants and the right of deposing kings’(Wight 1992: 11). Similarly, Calvin openly permitted the right of resistance by those organs of government entrusted with restraining Monarchical power, such as the Estates, and though he denied the right to kill a tyrant, he did suggest that resistance might be authorised by a representative council (Neumann 1957: 159). Furthermore, Calvin anticipated the Cromwellian rebellion of his intellectual heirs when he wrote that God restrains tyranny by either replacing the tyrant with another or by raising up within the community open avengers who rid the people of their tyrant (Calvin 1954: 31).

It was Calvin’s validation of the right of constitutionally enacted bodies to resist monarchical encroachment that led later Calvinist and Puritan thinkers to find in favour of tyrannicide. Knox, taking a liberalist view of Reformation principles like von Hutten, affirmed that it was the duty and even the right of the nation to condemn the Queen (Knox quoted in Lecky 1913: 164) and he defended the right to establish the true religion against the sovereign by force if necessary (Knox 1994: 3–47). The right of resistance was unquestioned in the interpretation of Calvinism by the Protestant Monarchomachs, such as in either Ponet’s or Goodman’s open defence of tyrannicide in England (Ponent1942), or in the theoretical defence of tyrannicide by Boucher and Languet in France (MacCaffrey 2007: Vol. I, Chapter VI). They held that a heretical prince was an outcast in the eyes of God and hence enjoyed no divine protection against tyrannicide (Ford 1985: 151). The most trenchant supporters of Calvin willingly declared war on tyrannies against God (Lecky 1913: 194 ff.) though their contemporary critics, Bodin and Barclay, argued that such resistance would more likely lead to further tyranny rather than freedom (Bodin 1992; Barclay1954).

Consequently, we see that throughout the medieval period that the consistent philosophical justification for tyrannicide was premised on natural law doctrines and yet that the consent or disapproval of God’s higher law was invoked with equal vigor on either side of the debate. In evaluating this model in terms of its adequacy for a contemporary theory of tyrannicide, a key benefit of natural law theory lies in its appeal to universality, the notion of an all-encompassing right of humanity that could validate all forms of resistance against breaches of natural justice by temporal leaders. Such a wide ambit would be of fundamental importance to help establish an international basis fora contemporary theory of tyrannicide. However, the appeal to natural law is a philosophical endeavor fraught with peril. The fundamental problem is that any right derived from a conception of natural law is impossible to objectify and thus philosophically arbitrary.

https://dhspriory.org/thomas/Sent2d44q2a2.htm I Sent., D. 44, Q. 2, A. 2 Utrum Christiani teneantur obedire potestatibus saecularibus, et maxime tyrannis	Thomas Aquinas’ Commentary on the Sentences of Peter Lombard,  Distinction 44, Question 2, Article 2 Whether Christians are bound to obey secular powers, especially tyrants
Ad secundum sic proceditur. Videtur quod Christiani non teneantur saecularibus potestatibus obedire, et praecipue tyrannis.	The procedure in discussing this problem is this: It seems that they are not bound to obey secular powers, especially tyrants.
Matth. 17, 25, dicitur: ergo liberi sunt filii. Si enim in quolibet regno filii illius regis qui regno illi praefertur, liberi sunt, tunc filii regis cui omnia regna subduntur, in quolibet regno liberi esse debent. Sed Christiani effecti sunt filii Dei; Roman. 8, 16: ipse enim spiritus testimonium reddit spiritui nostro quod sumus filii Dei. Ergo ubique sunt liberi; et ita saecularibus potestatibus obedire non tenentur.	1. Matthew 17:25 says: “Therefore the sons are free.” If then in any kingdom the sons of its king are free, then the sons of the king to whom all kingdoms are subject ought to be free in any kingdom. But Christians have been made sons of God —Romans 8:16: “The Spirit bears testimony to our spirit that we are sons of God.” Therefore they are free everywhere, and are not held to obey secular powers.
Praeterea, servitus pro peccato inducta est, ut supra, quaest. 1, art. 1, dictum est. Sed per Baptismum homines a peccato mundantur. Ergo a servitute liberantur; et sic idem quod prius.	2. Besides, slavery is the result of sin, as was shown above, q. 1, a. 1. But by Baptism people are cleansed from sin. Therefore they are liberated from slavery, and the same conclusion folows.
Praeterea, majus vinculum absolvit a minori, sicut lex nova ab observantia legis veteris. Sed in Baptismo homo obligatur Deo, quae obligatio est majus vinculum quam id quo homo obligatur homini per servitutem. Ergo per Baptismum a servitute absolvitur.	3. Besides, a greater bond frees one from a lesser one, as the new law frees from observance of the old law. But by baptism a man comes under obligation to God, which is a greater bond that that of man to man by slavery. Therefore by baptism he is freed from slavery.
Praeterea, quilibet potest licite resumere, cum facultas adest, quod sibi injuste ablatum est. Sed multi saeculares principes tyrannice terrarum dominia invaserunt. Ergo cum facultas rebellandi illis conceditur, non tenentur illis obedire.	4. It is legitimate for anyone, who can do so, to re-take what has been taken away from him unjustly. Now many secular princes unjustly usurped the dominion of Christian lands. Since, therefore, in such cases rebellion is legitimate, Christians have no obligation to obey these princes.
Praeterea, nullus tenetur ei obedire quem licite, immo laudabiliter potest interficere. Sed Tullius in libro de officiis salvat eos qui Julium Caesarem interfecerunt, quamvis amicum et familiarem, qui quasi tyrannus jura imperii usurpaverat. Ergo talibus nullus tenetur obedire.	5. If it is a legitimate and even a praiseworthy deed to kill a person, then no obligation of obedience exists toward that person. Now in the Book on Duties [De Officiis I, 8, 26] Cicero justifies Julius Caesar’s assassins. Although Caesar was a close friend of his, yet by usurping the empire he proved himself to be a tyrant. Therefore toward such powers there is no obligation of obedience.
Sed contra, 1 Petri 11, 18: servi subditi estote dominis vestris.	Sed C. 1. On the other hand, however, there are the following arguments proving the contrary position: First, it is said: Servants, be in subjection to your masters (1 Pet. 2:18.)
Praeterea, Rom. 13, 2: qui potestati resistit, Dei ordinationi resistit. Sed non est licitum Dei ordinationi resistere. Ergo nec saeculari potestati resistere licet.	Sed C. 2. Second, it is also said: He who resists the power, withstands the ordinance of God (Rom. xiii, 2.) Now it is not legitimate to withstand the ordinance of God. Hence it is not legitimate either to withstand secular power.
Respondeo dicendum, quod sicut dictum est, obedientia respicit in praecepto quod servat, debitum observandi. Hoc autem debitum causatur ex ordine praelationis, quae virtutem coactivam habet, non tantum temporaliter sed etiam spiritualiter propter conscientiam, ut apostolus dicit Roman. 13, secundum quod ordo praelationis a Deo descendit, ut apostolus, ibidem, innuit. Et ideo secundum hoc quod a Deo est, obedire talibus Christianus tenetur, non autem secundum quod a Deo praelatio non est.	Solution and determination. Obedience, by keeping a commandment, has for its [formal] object the obligation, involved in the commandment, that it be kept. Now this obligation originates in that the commanding authority has the power to impose an obligation binding not only to external but also to internal and spiritual obedience—“for conscience sake”, as the Apostle says (Rom. xiii, 5.) For power (authority) comes from God, as the Apostle implies in the same place. Hence, Christians are bound to obey the authorities inasmuch as they are from God; and they are not bound to obey inasmuch as the authority is not from God.
Dictum est autem, quod praelatio potest a Deo non esse dupliciter: vel quantum ad modum acquirendi praelationem, vel quantum ad usum praelationis.	Now, this not being from God may be the case, first, as to the mode in which authority is acquired, and, second, as to the use which is made of authority.
Quantum ad primum contingit dupliciter: aut propter defectum personae, quia indignus est; aut propter defectum in ipso modo acquirendi, quia scilicet per violentiam vel per simoniam, vel aliquo illicito modo acquirit.	Concerning the first case we must again distinguish two defects: There may be a defect of the person acquiring authority inasmuch as this person is unworthy of it. There may also be a defect in the mode of acquiring authority, namely, if it is obtained by violence, or simony, or other illegitimate means.
Ex primo defectu non impeditur quin jus praelationis ei acquiratur; et quoniam praelatio secundum suam formam semper a Deo est (quod debitum obedientiae causat); ideo talibus praelatis, quamvis indignis, obedire tenentur subditi.	As to the first of these defects, we say that it does not constitute an obstacle against acquiring lawful authority. Since, then, as such, authority is always from God (and this is what causes the obligation of obedience), the subjects are bound to render obedience to these authorities, unworthy as they may be.
Sed secundus defectus impedit jus praelationis: qui enim per violentiam dominium surripit non efficitur vere praelatus vel dominus; et ideo cum facultas adest, potest aliquis tale dominium repellere: nisi forte postmodum dominus verus effectus sit vel per consensum subditorum, vel per auctoritatem superioris.	As to the second of those defects, we say that in such a case there is no lawful authority at all. He who seizes power by violence does not become a true holder of power. Hence, when it is possible to do so, anybody may repel this domination, unless, of course, the usurper should later on have become a true ruler by the consent of the subjects or by a recognition being extended to him by a higher authority.
Abusus autem praelationis potest esse dupliciter: vel ex eo quod est praeceptum a praelato, contrarium ejus ad quod praelatio ordinata est, ut si praecipiat actum peccati contrarium virtuti ad quam inducendam et conservandam praelatio ordinatur; et tunc aliquis praelato non solum non tenetur obedire, sed etiam tenetur non obedire, sicut et sancti martyres mortem passi sunt, ne impiis jussis tyrannorum obedirent:	The abuse of power might take on two forms. First, a commandment emanating from the authority might be contrary to the very end in view of which authority is instituted, i.e., to be an educator to, and a preserver of, virtue. Should therefore the authority command an act of sin contrary to virtue, we not only are not obliged to obey but we are also obliged not to obey, according to the example of the holy martyrs who preferred death to obeying those ungodly tyrants.
vel quia cogunt ad hoc ad quod ordo praelationis non se extendit; ut si dominus exigat tributa quae servus non tenetur dare, vel aliquid hujusmodi; et tunc subditus non tenetur obedire, nec etiam tenetur non obedire.	The second form of abusing power is for the authority to go beyond the bounds of its legal rights, for instance, when a master exacts duties which the servant is not bound to pay, or the like. In this case the subject is not obliged to obey, but neither is he obliged not to obey.
Ad primum ergo dicendum, quod illa praelatio quae ad utilitatem subditorum ordinatur, libertatem subditorum non tollit; et ideo non est inconveniens quod tali praelationi subjaceant qui per spiritum sanctum filii Dei effecti sunt. Vel dicendum, quod Christus loquitur de se et suis discipulis, qui nec servilis conditionis erant, nec res temporales habebant, quibus suis dominis obligarentur ad tributa solvenda; et ideo non sequitur quod omnis Christianus hujusmodi libertatis sit particeps, sed solum illi qui sequuntur apostolicam vitam, nihil in hoc mundo possidentes, et a conditione servili immunes.	Ad 1. In answer to the first, authority which is instituted for the utility of the subjects does not take away their liberty. Therefore there is no problem in being subject to such authority for those who have become sons of God by the Holy Spirit. Or another answer could be: Christ is speaking about himself and his disciples, who were not of servile condition, nor did they have temporal property by which they would be obliged to pay tax to their lords. Therefore it does not follow that every Christian shares in this liberty, but only those who follow the apostolic life, owning nothing in this world, and unaffected by servile state.
Ad secundum dicendum, quod Baptismus non delet statim omnes poenalitates ex peccato primi parentis consequentes, sicut necessitatem moriendi et caecitatem, vel aliquid hujusmodi; sed regenerat in spem vivam illius vitae in qua omnia ista tollentur; et sic non oportet ut aliquis statim baptizatus a servili conditione liberetur, quamvis illa sit poena peccati.	Ad 2. In answer to the second, baptism does not delete all the penalties arising from the sin of the first parent, such as the necessity to die, or blindness, or the like, but it gives rebirth into a living hope of that life in which all those things are taken away. So someone just baptized need not be immediately liberated from a servile state, even though that is a penalty of sin.
Ad tertium dicendum, quod majus vinculum non absolvit a minori, nisi quando non compatitur se cum illo; sicut umbra et veritas simul esse non possunt: propter quod veniente veritate Evangelii, umbra veteris legis cessavit. Sed vinculum quo in Baptismo quis ligatur, compatitur vinculum servitutis; et ideo non absolvit ab illo.	Ad 3. In answer to the third, the greater bond does not free from the lesser unelss it is incompatible with it; thus shadow and truth cannot coexist, because when the truth of the Gospel came, the shadow of the old law ceased. But th bond taken on by baptism is compatible with servitude, and therefore it does not dissolve it.
Ad quartum dicendum, quod qui per violentiam praelationem accipiunt, non sunt veri praelati; unde nec eis obedire tenentur subditi nisi sicut dictum est.	Ad 4. To the fourth argument the answer is this: An authority acquired by violence is not a true authority, and there is no obligation of obedience, as we said above.
Ad quintum dicendum, quod Tullius loquitur in casu illo quando aliquis dominium sibi per violentiam surripit, nolentibus subditis, vel etiam ad consensum coactis, et quando non est recursus ad superiorem, per quem judicium de invasore possit fieri: tunc enim qui ad liberationem patriae tyrannum occidit, laudatur, et praemium accipit.	Ad 5. To the fifth argument the answer is that Cicero speaks of domination obtained by violence and ruse, the subjects being unwilling or even forced to accept it and there being no recourse open to a superior who might pronounce judgment upon the usurper. In this case he that kills the tyrant for the liberation of the country, is praised and rewarded.