Part of the issue with the New Perspective on Paul (NNP) is that this group of scholar reads Paul’s “works of the law” as being equivalent to “Judaism.” As Stephen Westerholm points out, the NNP scholars project their scholarly interpretation of what they think first century Judaism was like onto Paul’s statements about the “works of the law.” Of course, if one takes this line what Paul says about the law makes no sense, since it posits that first century Judaism was a “religion of grace” or, really, a religion that mixed grace with law. As a result, NNP scholars think that Paul must “really mean” to criticize first century Judaism for not knowing that the covenant signs of the old dispensation don’t really apply anymore. But Paul doesn’t make his point mysterious at all. In Galatians 3, he explains what he means by the “works of the law.” Namely, he refers to the Sinaitic covenant. Hence, all his statements about the law have nothing to do with Judaism or the empirical religion of Israel in the OT period. They have to do with the logic of reward and punishment that Sinaitic covenant establishes.
Crux sola est nostra theologia