15 "We who are Jews by birth and not sinful Gentiles 16 know that a person is not justified by observing the law, but by faith in Jesus Christ. So we, too, have put our faith in Christ Jesus that we may be justified by faith in Christ and not by observing the law, because by observing the law no one will be justified.There are many things that could be said about justification in this passage. Certainly there is a strong affirmation of justification being by faith and an emphasis on a corporate aspect of justification. What I'd like to point out in this post, though, is the time of justification.
17 "But if, in seeking to be justified in Christ, we Jews find ourselves also among the sinners, doesn't that mean that Christ promotes sin? Absolutely not! 18 If I rebuild what I destroyed, then I really would be a lawbreaker.19 "For through the law I died to the law so that I might live for God. 20 I have been crucified with Christ and I no longer live, but Christ lives in me. The life I now live in the body, I live by faith in the Son of God, who loved me and gave himself for me. 21 I do not set aside the grace of God, for if righteousness could be gained through the law, Christ died for nothing! (TNIV)
Traditionally Reformed theology has a very strict ordo salutis in which justification is one piece of the puzzle in salvation (see Redemption Accomplished and Applied by John Murray for a standard Calvinist presentation). It occurs at after one is born again and is the one time declaration by God that one is not guilty. The status that one receives because of the future not guilty verdict is 'justified.' There are passages like Romans 8:29-30 that might suggest the appropriateness of this type of scheme. Here, justification is understood to be a past event in the life of the believer.
I don't know if that will hold up when we look at how Paul talks about justification in this passage (my debt here is to Doug Moo in a lecture at Denver Seminary - though he didn't mention this specific passage). The first occurrence of 'justified' in verse 16 is a present indicative - thus justification is present. The second is an aorsit subjunctive, which means that there is no significance of time. The third occurrence, however is a future indicative. Justification, while not being by works, is something that happens in the future.
What is the primary sense of justification? I don't think we can answer that very easily. Each text has to be taken on a case by case basis being careful not to read in our understanding of justification that comes from systematic theology. Perhaps a fruitful way to go forward would be to examine what Paul is trying to do pastorally through talking about justification. That may help us see how past/present/future justification is understood to impact the believer in the present.
In the present text I think that Paul's uses in the first and third case (the two that involve time) are related. In the first he affirms that one is not justified (and hence part of the people of God - presently) by works. The third case affirms that final vindication does not come by faith. Both function similarly because they are phrased negatively (how one isn't justified) which I think shows that there is a close relation between justification in the present and justification on the last day. How close? I'll answer that in my 'Judgment and Justification' series.