Is promulgation part of the nature of law?

It seems that promulgation is not part of the nature of law:

Objection 1:  Natural law especially has the nature of law.  But natural law does not require promulgation.  Therefore, it is not part of the nature of law that it be promulgated.

Objection 2:  Properly speaking, law plays the role of obligating someone to do or not to do something.  But it is not just those to whom a law is promulgated who are obligated to fulfill the law; the others are obligated as well.  Therefore, promulgation is not part of the nature of law.

Objection 3:  The obligatory force of law extends even into the future, since, as jurists say, laws impose necessity on future transactions.  But promulgation is made [only] to those who exist at present.  Therefore, law does not require promulgation.

But contrary to this:  Decretals, dist. 4, says, “Laws are instituted when they are promulgated.”

I respond:  As has been explained (a. 1), law is imposed on others in the manner of a rule and measure.  But a rule or measure is imposed by being applied to the things that are ruled and measured.  Hence, in order for a law to acquire the power to obligate, which is proper to law, it must be applied to the men who are supposed to be regulated by it.  Now this sort of application is accomplished by the law’s being brought to their knowledge through its promulgation.  Hence, promulgation is necessary in order for the law to have its power.
And so from the four traits that have been mentioned, we can put together a definition of law:   Law is (a) an ordinance (ordinatio) of reason, (b) for the common good, (c) made by one who is in charge of the community, and (d) promulgated.

Reply to objection 1:  The promulgation of the law of nature consists in God’s having instilled it in the minds of men in order that they might know it naturally.

Reply to objection 2:  Those who are such that the law is not promulgated in their presence are obligated to follow the law insofar it is or can be brought to their knowledge through others, once the promulgation has been made.

Reply to objection 3:  A present promulgation extends into the future by reason of the permanence of writing, which in some sense continually promulgates the law.  Hence, in Etymologia 2 Isidore says,  “ ‘Law’ (lex) is derived from reading (legendo), because it is written.”