So then why use these seeming terms of imprisonment and guarding, which seem to contradict the next thing Paul says about Law: that it is a Paidagos? The NRSV translates this word as disciplinarian, which fits with the negative understanding of the guarding words, the NRSV translates in terms of imprisonment. However, there is a clear cultural referent in paidagogos as the servant who attended and guarded privileged children to the gymnasium (school). According to Liddel and Scott "tutor" would be the English for paidagogos. A paidagogos was a slave or servant who attended and guarded a child, a son in the cultural context, on his way to and from the gymnasium and was in charge generally of watching over the son's education. This son would also be an heir and the training of the son as a child would be training him to inherit the fathers estate and business etc. Only male children need these "tutors", and once they were adults and fully heirs the sons are simply sons of the father free from the discipline of a paidagogos.
I believe we and the NRSV translators get tripped up here by the fact that Paul uses an illustration from a privileged and thus to us oppressive system,(Classist and Patriarchal) to illustrate our relationship to God in and through Jesus Christ. Here is how I read Paul's metaphor: The Law guarded us and protected us like privileged Greek male children are guarded and attended by a tutor, who is a slave of the son's father. The paidagos serves the father, the Law serves God. But once Christ came we all have become adults, we are son's of the father. We are all heirs. Paul makes this explicit in the end of the passage where he says we are all heirs of Abraham, of the promise.
In my estimation for us to interpret correctly and by interpret I mean not say only what Paul meant but what it can mean for us, we actually have to hear this as a metaphor drawn from privilege. We need to hear the gendered, sons of God. In neutralize the gendered language by saying we are "children of God" we hide that Paul is talking about an adult child who has received full privilege of his adult status as heir of the father's estate. Paul in essence queers things: woman, slaves, those others(we don't like) are as much heirs as we whom we like, the privileged, and men. Paul uses an extend metaphor based in the oppressive system of the world to show us how in Christ all of that is turned around and to show us that the proper function of the Law was to prepare us for Christ and our role in Christ as sons, that is heirs.
Humanity was closely guarded by the Law as our custodian/tutor, and like a son once an adult no longer needs a paidagagos, but who has been guarded and attended so as to be able to become the adult son who will inherit. So, it would be rediculous for a son to as an adult continue to submit to a paidagagos, so it is a denial of Christ to submit to the law after Christ, for we are all heirs and sons in Christ Jesus, through our identification with Jesus Christ.
The upset the upheaval all happens in Jesus Christ and because of Jesus Christ. Paul's statement about "no longer Jew or Greek... slave or free,... male or female" isn't based in some generic inclusive humanity, but that Christ is the true human, is humanity. We find our place again as human beings not in our origin, Adam or Abraham, but in Christ Jesus. Our identity must become one with Christ. The reality happens in unification with Christ not some cultural evolution, for Jesus Christ is humanity come of age. Sorry Bonhoeffer the coming of age of humanity, if I am reading Paul correctly here, happened in Jesus Christ, not European enlightenment and World War. Humanity isn't' evolving towards greater consciousness, it has achieved this adulthood and consciousness in Jesus Christ, and it is only in unity with Christ that we come of age and become heirs, that is sons of God, no matter who we are what our gender, what our class, what our race or ethnicity. This is a radical message of Christ who is all in all, not about human achievement or cultural evolution. If it could be human achievement and cultural evolution then we are simply back in some kind of "Law" it may not be the Torah (and that is probably worse than dependence on Torah which actually came from God, after the promise) but it would still be a law, that human beings can advance because of their inherent humanity. This Paul preaches against because such views of improvable humanity make a mockery of the life death Resurrection and ascension of Jesus Christ.