Is not Spirit of God the giver of our faith, and is not the Spirit of God the motivator of our faith in Him?
That's not off topic. It's the answer to your question of "we establish the law....but how?"
Romans 3:27-30
27 Where is boasting then? It is excluded . By what law? of works? Nay: but by the law of faith.
28 Therefore we conclude that a man is justified by faith *without the deeds of the law.
29 Is he the God of the Jews only? is he not also of the Gentiles? Yes, of the Gentiles also:
30 Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith.
"without" 5565. choris kho-rece' adverb from 5561; at a space, i.e. separately or apart from (often as preposition):--beside, *by itself, without.
"deeds" 2041. ergon er'-gon from a primary (but obsolete) ergo (to work); toil (as an effort or occupation); by implication, an act:--deed, doing, labour, work.
As I had mentioned before, Paul is using "circumcision" as a focus of describing the law in chapter 3 in Romans. I had also mentioned that the law says that Circumcision is supposed to be of the heart to alleviate being stubborn or "stiffnecked."
It is important to note that Romans 3:28 is clear that the deeds of the law "*by itself" are not what makes a person justified. Faith comes first through the spirit and is the motivator to establish the law. The sequence of events come from God. I think I see your motivation of teaching an interpretation of scripture that you want to be true, but isn't.
"We" are included and exhorted to respond responsibly to these things according to Romans 3:31 as a summary of the entire chapter.
So I end trying to help you to understand "how" with this. We receive faith by the Spirit of God. We are to use that faith to establish the law given by God not by separate deeds of the law minus faith, but by the motivating Spirit of God. If the law cannot be established, then the motivation isn't there. What do you think that says?
In order of accomplishment. All capability comes from above.
1. Spirit
2. Faith
3. Establishment is successful
In that order. Is there something that you don't understand about Paul including himself with ourselves in the said verse when he says "we"? He is exhorting us to insert "self". ourselves.
"Do we then make void the law through faith? God forbid : yea, we establish the law."
WHEE!!