In chapter 6, Fesko focuses on 'Justification In It's Historical Context' with particular attention paid to the New Perspective on Paul (NPP). Central to the NPP was Ed Sanders work on Second Temple Judaism in 1976. Sanders contended that, contrary to traditional Reformed exegesis, the Jews of the NT period were not legalists, i.e. trying to justify themselves before God by law-keeping. No, said Sanders, the Jews believed in grace. They believed that they were elected to salvation by grace and 'stayed in' the covenant by obedience to the law. Sanders would point out that the law never required perfect obedience since atonement for sin was built in to the covenantal framework to cover those with less than perfect obedience.
Others, including most notably N.T Wright, developed this further by saying that if the Judaism of Paul's day was not a self-help legalism, then the context in which Paul framed his doctrine of justification was different than that assumed by traditional Protestant exegetes. As a result, the doctrine of justification was not about 'how someone gets saved' by grace as opposed to by law keeping. No, according to NTW, justification was about who belonged to God's covenant community.
Again, according to NTW and Dunn, the Jews were not legalists but racists who wanted to keep the Gentiles from experiencing God's salvation (and to think the NPP was supposed to save the church from anti-Semitism!). The argument goes that when Paul spoke of justification apart from 'works of the law' he was not speaking about keeping the law in order to be saved. No, says NTW, 'works of the law' speak of the badges of who's in the covenant, i.e. badges of Jewishness like circumcision, Sabbath keeping, etc. According to Wright, faith is the only covenant badge post-Calvary, so therefore Gentiles can be included in the people of God. So Wright believes that justification is about ecclesiology, i.e. who is part of the church, as opposed to soteriology i.e. how you come into saving relationship with God. The implications of this are huge and I don't have time to go into them here.
Safe to say, Fesko gives this daft view a proper kicking in chapter 6. Works of the law clearly means obedience to the law as a whole.
One of the more valuable insights he provides is NTW's inability to deal with the 'works' passages in Ephesians 2. Works do indeed seem to be equated to legalism in this chapter as opposed to justification. NTW recognises this,but attempts to get around this by pointing out that Paul in Ephesians speaks of 'salvation' not 'justification' and that Paul only contrasts legalistic righteousness with the word 'salvation'. So Wright is able to tenuously hold onto the claim that racism is the polemical backdrop to the word 'justification'. I'll let Fesko have the last word:
While it is certainly possible to distinguish justification from salvation, they cannot be separated. Contra Wright, whether one wants to speak of justification, an element within the broader picture of salvation, by works, or salvation by works, Paul rejects both. Moreover, in the overall flow of Paul's argument in Ephesians 2 he deals with the same issues as in Romans and Galatians, namely the salvation of both Jews and Gentiles by faith alone, not works. (p184)