The word jus, signifying right, is derived from the Latin word jussus, because it implies a power of some authority, commanding this or that to be done.
It is therefore taken:
First, for the Law commanding.
Secondly, for the object and effect of justice, or for the action itself, prescribed and required by law; and in this sense we are said to give every man his right.
Fourthly, for the power which any man hath to do this or that according to law, in which sense we usually say, Such a man stands upon his right. And not unlike to this acceptation is the applying of the same word to denote some particular privilege granted to any man, either by law or just authority.
This word right in its largest acceptation is divided into: divine, of which God is the author; human, of which man is the contriver.
Divine right is divided into right natural, and right positive.
Right natural is that which is apprehended to be fit to be done or avoided, out of the natural instinct of natural light; or that which is at least deduced from that natural light by evident consequence. So that this right partly consists of practical principles known by nature, and partly of conclusions deduced from those principles.
The divine positive right is a right added to the natural by some special revelation of God.
The right natural, or natural law, is the same which usually is called the eternal law. But it is called eternal in relation to God, as it is from eternity in him. It is called natural as it is engrafted and imprinted in the nature of man by the God of nature.
That positive right was in the mind of God from eternity, as well as the natural. But in respect it is not so easily apprehended by human reason, therefore it is not usually termed the law eternal.
The natural and positive divine right differ in this: that the positive is mutable and various according to God’s good pleasure (for that which was heretofore in the Judaical church is different from that which is in the Christian church); but the right natural is always the same and like itself, and for this reason also it is called the law eternal.
Question 3: Whether it be rightly said by lawyers, that the right natural, or the law of nature is that which nature hath taught all living creatures?
In brute creatures the true nature of right or law hath no more place than it hath in plants or things inanimate. For neither is there a reason distinguishing between good and evil, neither a will or choice of one thing before another; nor, lastly, any justice at all in brutes more than in things without all life. Nevertheless, in all things there is an inclination, a power and operation, which is guided by certain reason forasmuch as concerns their nature and end. And in this respect all things created are said to have a law prescribed unto them, so that in respect to themselves it is only by similitude and some proportion termed a law or right (Psalm 148. 6; Job 38. 10-12; Jer. 33. 20, 25). * * *
Question 4: Whether the Law of Nations be the same with the Law of Nature?
The law of nations, as it is taken for the law which all nations use, comprehends under it not only the law of nature but also the positive law. So servitude is by lawyers said to be by the law of nations, and yet [it] is evident that servitude was brought in by custom and the positive law. And the same is the reason in division of possessions, and the like.
If the law of nations be taken for that law which is introduced by the common consent and custom of all nations, it then participates in a certain middle nature between the law natural and that positive law which is peculiar to this or that nation. It hath thus much common with the natural law, that it is everywhere received without any certain authority or promulgation, and wheresoever anything is done contrary it is censured of all men to be ill done. And it hath thus much common with the positive law, that it may be changed or abrogated by the common consent of them whom it may concern. A division of things is by the law of nations. Nevertheless, by the common consent it may, upon just grounds, be somewhere enacted that almost all possessions should be in common.
Question 5: Whether the precepts of the Law of Nature be rightly stated: To live honestly; not to hurt another; to give every man his due?
This enumeration is somewhat confused and imperfect. For first, here is nothing mentioned of the worshipping of God, which nevertheless is a principle of the law of nature.
Question 6: Whether that precept be of the Law of Nature: What you would have done to yourself, do that to another . . . ?
This precept is natural, and indeed divine (Matt. 7. 12; Luke 6.  31). Yet in this it is to be observed: First, that this law doth not include the whole compass of the natural law in general, but that part only in which our duty between man and man is comprehended; secondly, that our will whatsoever it be, may not be the square and rule of the performance of our duty to others . . ., but our natural will being well disposed, and not tainted with any passion or perturbation, by which we truly and considerately wish good unto ourselves.
Question 7: What proportion the Civil Law holds with the Law of Nature?
The civil law is that which every city or society of men enacts current for itself. And such a kind of law is not only peculiar to the Romans, but also to the Athenians, English, or any else who have no respect to the Roman law.
This civil law inasmuch as it is right is derived from the law of nature; for that is not law which is not just and right, and that in morality is called right which accords with right practical reason, and right practical is the law of nature.
This civil law therefore is derived from the law of nature, either as a special conclusion inferred from a general proposition or as a special determination and application of a general axiom.
That law which is derived from the natural law only by way of conclusion, if the consequence be good, hath its whole strength from the law of nature, as the conclusion hath its force from the premised propositions; but that which is derived from the law of nature by way of determination and application, is in part a new constitution, even as every species hath its own proper form and essence besides that which is actually comprehended in the genus.
Seeing then that, as well in conclusions as determinations, the reason of man can only imperfectly judge—nay, and is often therein cozened—hence it must needs follow that all human constitutions are of necessity liable to imperfection, error, and injustice. This the authors of the Roman law confess of their own laws: ‘It is impossible that a reason should be given of all things that are enacted—not to all men, nor of all the laws—and it is proved in innumerable cases that there are many things received in the civil law for the public good, which are somewhat contrary to a disputative reason’ .
The imperfection of the best civil law consisteth in this. First, in regard, it contains not in its compass the whole law of nature, but so much of it only as such or such men have approved and thought appliable to their own manners; secondly, in respect, it hath no eye at all upon the inward affections, but only upon the outward actions; for it doth not suppress absolutely all vices, but those only which may seem likely to disturb the peace and quiet of the commonwealth, neither doth it enjoin all acts of all virtues, but those only which are opposite to the inconvenient vices; thirdly, in that it doth not principally make good men, but only good subjects or citizens; fourthly, in that upon occasion it may admit in many things of addition, detraction, or correction.
Question 8: What proportion the Moral Law bears to the Law of Nature?
All the precepts of the Moral Law are out of the law of nature, except the determination of the sabbath day in the Fourth Commandment, which is from the positive law.
For first, we meet with nothing in them which concerneth not all nations at all times, so that these precepts do not respect any particular sort of men, but even nature itself. Secondly, nothing is contained in them which is not very necessary to human nature for the attaining of its end. Thirdly, there is nothing in them which is not so grounded upon right reason but it may be solidly defended and maintained by human discourse; nothing but what may be well enjoined from clear reason. Fourthly, all things contained in them are for the substance approved, even of the more understanding sort of the heathen. Fifthly, they all much conduce to the benefit of mankind in this present life; insomuch that if all these precepts were duly answered, there would be no need of any other human laws or constitutions.
Object[ion]: But it may be objected that if the Moral [Law] were the same with the law of nature, it had no need to be promulgated either by voice or writing, for it would have been writ in the hearts of all men by nature.
Answer: That to nature upright, i.e., as it was in the state of innocency, there was no need of such a promulgation. But ever since the corruption of our nature, such is the blindness of our understanding and perverseness of our will and disorder of our affections, that there are only some relics of that law remaining in our hearts, like to some dim aged picture, and therefore by the voice and power of God it ought to be renewed as with a fresh pencil. Therefore is there nowhere found any true right practical reason, pure and complete in all parts, but in the written law of God (Psalm 119. 66).
Question 9: What proportion the Judicial Law bears to the Natural?
That is properly termed the Judicial which is about judgments or any politic matters thereto belonging, as that was called the Ceremonial Law which was about ceremonies, and that the Moral Law which was about manners and civil duties. That Judicial Law which was given by Moses to the Israelites as proper only to them, was a most exact determination and accommodation of the law of nature unto them, according to the particular condition of that people. To the Israelites therefore in respect of the use, it was of like nature with other good civil laws among other nations; but in respect of authority, which from God, the immediate giver, it received, it was of much more perfection than any. This law belongeth not to Christians under the title of a law especially obliging them, but only by way of doctrine, inasmuch as in its general nature, or in its due proportion to it, it doth always exhibit unto us the best determination of the law of nature.
Those laws were properly termed Judicial, which being not ceremonial, had some singular respect to the people of the Jews, so that the whole reason and ground of them was constituted in some particular condition of that nation. But it is no certain rule (which is given by some) that wheresoever the reason of the law is moral, there the law itself is moral (as is seen in Lev. 11. 44), for any special determination of a law may be confirmed by a general reason. . . . But where the special intrinsical and proper reason of the law is moral, there it always follows that the law itself must needs be moral.
Those laws, therefore, which are usually reckoned among the judicial, and yet in their nature bear no singular respect to the condition of the Jews more than of any other people, those are all of the moral and natural laws which are common to all nations.
Jussus- order, command, decree, ordinance;
Source: William Ames, Conscience (1639)