Does every humanly made law stem from the natural law?

It seems that not every humanly made law stems from the natural law:

Objection 1:  In Ethics 5 the Philosopher says, “What is legally just is such that at the beginning it did not matter whether it was done this way or some other way.”  But in things that arise from the natural law it does matter whether they are done this way or some other way.  Therefore, not everything established by human laws stems from the law of nature.

Objection 2:  As is clear both from Isidore in Etymologia and from the Philosopher in Ethics 5, positive law (ius positivum) is opposed to natural law (ius naturale).  But as was explained above (q. 94, a. 4), what stems in the manner of a conclusion from the principles of the law of nature belongs to the law of nature.  Therefore, what belongs to human law does not stem from the law of nature.

Objection 3:  The law of nature is the same for everyone; for the Philosopher says in Ethics 5, “What is naturally just is such that it has the same force everywhere.”  Therefore, if human laws stemmed from the natural law, it would follow that these human laws are likewise the same for everyone.  But this is clearly false.

Objection 4:  A reason can be given for things that stem from the natural law.  But as the Legal Expert points out, it is not the case that a reason can be given for everything that those in charge (maiores) have established as law.  Therefore, not every human law stems from the natural law.

But contrary to this:  In his Rhetorica Tully says, “Fear and reverence sanctioned both what had come from nature and what had been approved by custom.”

I respond:  As Augustine says in De Libero Arbitrio 1, “A law which is not just does not seem to be a law at all.”  Hence, something has the force of law to the extent that it shares in justice.
Now in human affairs something is called just by virtue of its being right (rectum) according to the rule of reason.  But as is clear from what was said above (q. 91, a. 2), the first rule of reason is the law of nature.  Hence, every humanly made law has the character of law to the extent that it stems from the law of nature.  On the other hand, if a humanly made law conflicts with the natural law, then it is no longer a law, but the corruption of law.
Note, however, that there are two possible modes in which things can stem (derivari) from the natural law:  first, (a) as conclusions from principles, and, second, (b) as specifications (determinationes) of what is general.  The first mode is similar to the way in which demonstrative conclusions are produced from principles in the sciences.  By contrast, in the second mode there is a similarity to the way in which general forms are narrowed down to something more specific in the arts—for instance, a craftsman must narrow down the general form house to this or that specific shape for a house.
Thus, some things stem from the universal principles of the law of nature in the manner of a conclusion; for instance, One should not kill can be derived as a conclusion from One should not do evil to anyone.  On the other hand, some things are derived in the manner of a specification; for instance, the law of nature says Let him who does evil be punished, but it is a specification of the law of nature that an evildoer should be punished by this specific punishment.
Thus, both sorts of things are found posited in human law.  However, what stems from the natural law in the first mode is not contained in human law in such a way that it is posited by that law alone; rather, it also has some of its force from the natural law.  By contrast, what stems from the natural law in the second mode has its force from human law alone.

Reply to objection 1:  In this passage the Philosopher is talking about what is posited by the law through a determination or specification of the precepts of the law of nature.

Reply to objection 2:  This argument goes through for the case of those things that stem from the law of nature as conclusions.

Reply to objection 3:  Because of the great variety in human affairs, the general principles of the law of

nature cannot be applied in the same way to everyone.  This is the source of the diversity of positive law for diverse people.

Reply to objection 4:  This passage from the Legal Expert should be understood as applying to what is introduced by those in charge concerning particular specifications of the natural law.  The judgment of men who are experienced and prudent bears the same relation to these specifications as it does to the principles—viz., that they see directly what particular specifications are appropriate.  Hence, the Philosopher says in Ethics 6 that in such matters “one should give no less respect to the indemonstrable pronouncements and opinions of experienced and older and prudent men than to demonstrations.”