Is law always ordered toward the common good as its end?

It seems that law is not always ordered toward the common good (bonum commune) as its end:

Objection 1:  It is law’s function to command and forbid.  But precepts are ordered toward certain individual goods (singularia bona).  Therefore, law does not always have the common good as its end.

Objection 2:  Law directs a man toward acting.  But human acts have to do with particular matters.  Therefore, law is likewise ordered toward a certain particular good (particulare bonum).

Objection 3:  In Etymologia Isidore says, “If law is founded upon reason, then law will consist of everything that is founded upon reason.”  But it is not just what is ordered toward the common good that is founded upon reason, but also what is ordered toward one’s private good.  Therefore, law is ordered not only toward the common good, but also toward one’s private good.

But contrary to this:  In Etymologia 5 Isidore says, “Law is formulated not for any private advantage, but for common benefit of the citizens.”

I respond:  As has been explained (art. 1), by virtue of the fact that law is a rule and measure, it has to do with the principle of human acts.  Now just as reason is the principle of human acts, so too within reason itself there is something which is the principle with respect to everything else.  Hence, this must be what law is principally and especially concerned with.
Now in actions, which practical reason is concerned with, the first principle is the ultimate end.  But, as was established above (q. 2, a. 7), the ultimate end of human life is happiness or beatitude.  Hence, law must have to do mainly with an ordering that leads to beatitude.
Again, since (a) every part is ordered toward its whole in the way that what is incomplete (imperfectum) is ordered toward what is complete (perfectum), and since (b) a man is part of a complete community, law must properly be concerned with the ordering that leads to communal happiness.  Hence, in the definition of legal affairs alluded to above, the Philosopher makes mention of both happiness and political union.  For in Ethics 5 he says, “The laws (legalia) we call ‘just’ are those that effect and conserve happiness and its elements within the political community.”  For as Politics 1 puts it, a city is a complete community.
Now in every genus, the genus is especially predicated of the thing that serves as the principle of the others, and the genus is predicated of the others because of their relation to that thing.  For instance, fire, which is maximally hot, is a cause of the heat in mixed bodies, which are called ‘hot’ to the extent that they participate in fire.  Hence, since ‘law’ is predicated especially in relation to the common good, it must be the case that any other precept about a particular act has the character of law only to the extent that it is ordered toward the common good.  And so every law is ordered toward the common good.

Reply to objection 1:  ‘Precept’ implies the application of law to the things that are regulated by the law.  But an ordering toward the common good, which law is concerned with, is applicable to individual ends.  Accordingly, precepts are likewise handed down with respect to certain particular matters.

Reply to objection 2:  Actions are, to be sure, concerned with particular matters.  However, those particular matters can be referred back to the common good—not, indeed, because they share with it a common genus or species, but rather because they share with it a common final cause.  This is why the common good is called a common end.

Reply to objection 3:  Just as nothing is firmly established through speculative reason except by being traced back to first indemonstrable principles, so too nothing is firmly established through practical reason except by being ordered to the ultimate end, which is the common good.  But what is founded upon reason in this way has the character of law.