T. David Gordon is a conservative modern day Reformed scholar and is friends with big name Reformed scholars such as John Fesko and R. Scott Clark. In a 2009 book The Law is Not of Faith, which included essays by various conservative Presbyterian theologians, Dr Gordon wrote an essay that included some important comments on Saint Paul's use of the term "Law" in his Epistles. These comments were so revealing that I was surprised hardly anyone raised an issue about them, and in fact I'm surprised they were even published in the book.
Since the time of the Reformers, Protestant scholars have interpreted "works of the Law" to be works done under God's eternal law when God made a perpetually binding Covenant of Works with mankind, starting with Adam in the Garden of Eden. Thus, in Paul's frequent use of the term "Law" in his Epistles, nomos in Greek, Protestants have historically said Paul is speaking of the Covenant of Works. But Gordon objects to this thesis, and in doing so undermines the entire foundation from which Protestants derive the doctrine of Justification by Faith Alone. Fortunately, this essay is available on his website, so those interested can read it for themselves. I will limit this post to quoting just the most important parts of Gordon's thesis.
Few contributions to Pauline studies in the last several decades are more important than the now widely-recognized lexical reality that for Paul, [ho nomos] means “the Sinai covenant,” far more consistently than it means anything else. As Douglas J. Moo has said: “What is vital for any accurate understanding of Paul’s doctrine of law is to realize that Paul uses nomos most often and most basically of the Mosaic law.”14 That is, Paul uses the term very differently than the term later came to be used in Christian theology, ordinarily to denote something like God’s demand. Again, Moo is right to correct this notion:In brief, what conservative Reformed scholars Gordon and Moo have admitted is that the Reformers and Protestantism as a whole completely butchered and misunderstood a crucial word/concept of Paul's teaching on justification. The Reformed tradition, with all its great minds and exegetes, has failed to understand a most basic tenet of Romans and Galatians, and in doing so has invented a new theology and new Gospel. Since nomos does not mean "God's demands in general," but rather the "Mosaic Law," this means that the Covenant of Works has no place in Paul's theology and instead projected onto the text! Realizing this, Reformed scholarship is now approaching a cross-roads where any Reformed scholar wanting to save their scholarly reputation must be honest enough to admit Protestantism has been wrong on this point from the beginning, and as a consequence admit Sola Fide is wrong as well.As we have seen, the Reformers, as most theologians today, use “law” to mean anything that demands something of us. In this sense, “law” is a basic factor in all human history; and man is in every age, whether in the OT or NT, confronted with “law.” What is crucial to recognize is that this is not the way in which Paul usually uses the term nomos.In no place is this distinctive use of nomos more obvious than in Galatians 3:17: “This is what I mean: the law, which came 430 years afterward [i.e. after Abraham], does not annul a covenant previously ratified by God, so as to make the promise void.” Note here that what is distinguished is the two covenant administrations spoken of throughout Galatians 3 and 4, covenant-administrations that are historically inaugurated 430 years apart from each other. (Pages 14-15)