Translating Paul can sometimes be incredibly difficult. Case in point: Romans 3:21. Here we find an important theme statement for Paul – yet there is little agreement as to exactly what he means.
Conversely, the TNIV reads like this: “But now apart from the law the righteousness of God has been made known…”
There is no small difference here. Is this verse praising God for his own glory or describing something that God has done for us? Both ideas are in play in Romans, of course, but your reading of the rest of Paul’s letter will be colored by what you take as Paul’s meaning here.
If you go with the NIV option, you likely agree with Luther, Calvin, and an assortment of other reformed scholars who believe that Romans is chiefly concerned with how we cannot achieve works-based perfection. We can only be “righteous” if God imputes his own righteousness on us.
NT Wright, a wide array of other “new perspective” scholars, and (it would seem) the TNIV translators, on the other hand, believe that “righteousness of God” makes perfect sense. Paul’s concern in Romans, they argue, is not to prove that absolute moral perfection by works is impossible. Nobody thought that. Not even the Judaizers, who advocated Gentile adherence to the law of Moses, were under the delusion that they were morally perfect.
Instead, they assert, Romans is concerned with God’s faithfulness to his promises. How will God honor his promise to bless all nations through Abraham? How will he deal with Israel’s unfaithfulness to their charge to be a light to the Gentiles? The “righteousness of God,” they argue, has been revealed for Paul: God has now come into human history to fulfill his promises.
The TNIV/Wright perspective makes more sense to me, at least insofar as I can follow the arguments. But I am not really qualified to be a participant in the debate.
The important thing to keep in mind, however, is that – under either perspective – 3:21 declares that it is only by God’s action (by either assigning to us his own righteousness OR by being faithful to his covenant) that it is possible for us to be justified.