Here, Carl Trueman is speaking about John Owen’s engagement with Richard Baxter, the fear that Baxter perceived to be a problem within Owen’s understanding of atonement. Without getting into that though, I wanted to offer up the way that Trueman explains the Covenant of Works (if for nothing, else, as a place for future reference). Here is Trueman:
. . . While later Protestants repudiated the Roman Catholic notion of grace, they nevertheless had to wrestle with precisely the issue of how infinite and finite can connect and, indeed, of how the finite can come to merit eternal rewards. Reformed theology from the late sixteenth century onward typically articulated this in terms of pre-fall Adam by use of the concept of the covenant of works: subsequent to creation, God entered into a covenant with Adam (as representative of his posterity) whereby he would reward Adam’s obedience by giving him eternal life and punish his disobedience by death. The key point is that the value of Adam’s obedience, as far as meriting eternal life goes, was not intrinsic but was the result of the extrinsic determination of God. Thus, in his massive Latin work, Theologoumena Pantodapa, Owen pointed out that it was only the freely constituted covenant of works which provided the framework by which Adam, a mere creature, could have achieved a supernatural end. God condescended to establish a covenant with Adam; and then Adam was able to claim a debt from God, but only by virtue of the divinely initiated and determined covenant. 
The covenant of works concept has not been without subsequent critics within the Reformed tradition, most notably John Murray, partly because the language of covenant is absent from the Genesis account. From a historical perspective, such criticism misses an important historical point: the covenant of works was not developed simply by exegeting Genesis 1 and 2; it arose more out of reflection on the Pauline epistles than on the creation account, still less the linguistically ambiguous Hosea 6:7. This is important because it points to the close connection in Reformed dogmatics between the covenant with Adam and the work of Christ. Representative headship is covenantally grounded and determined, and discussion of such headship must therefore be rooted in discussion of the nature and terms of the covenant. 
It is interesting, isn’t it? In the first paragraph I quote from Trueman he writes more pointedly this: “. . . Reformed theology from the late sixteenth century onward typically articulated this in terms of pre-fall Adam by use of the concept of the covenant of works: subsequent to creation, God entered into a covenant with Adam (as representative of his posterity) . . . .” It appears to me, that Trueman, and the trad are attempting to elide the idea that the covenant of works is somehow contingent upon creation; and instead, attempt to articulate it in a chronological way that keeps the covenant of works back up in a doctrine of God (albeit in a kind of voluntaristic conception of God; i.e. the covenant is an arbitrary choice of God, but not necessarily God in act with His person, necessarily). But one of many problems with this ‘order’ and proposal, is that it still allows the finite creature, Adam, to shape how God relates to His creation. In other words, even if the covenant of works is somehow, chrono-logically prior to Genesis 1:1, it is still made in a world wherein creation helps to determine how God will act in relation with His creation. Furthermore, it is interesting, by placing the covenant of works prior to the act of actual creation, and by placing Adam into this scenario of covenant, prior to the act of creation, what this offers us is an abstract conception of Adam (humanity) that serves more as a cipher for articulating a voluntaristic covenant of God; or, it conceives of humanity dualistically, or neo-Platonically, as if there was a pre-created-Adam (i.e. the ‘eternal form’) with whom God walked (in the scheming of the covenant of works), prior to an actual personage of Adam in concrete and actual creation.
I have not even broached the problem of ‘merit’ associated with this scheme yet. And I did, implicitly note how God’s act is ruptured from His person in this Federal or Covenantal scheme of covenant-making. But I will have to get into this further at a later date.
Edit is forthcoming. For some reason I totally mis-read the quote from Trueman (I’ll blame it on the fact that I work graveyard, and tired all the time), wrongly. I thought it was reading rather strangely, and I have no idea why I thought it read the way it does. Anyway, I will re-write and offer an edit on this below; based on the correct reading 🙂 .
Re-write: The problem with historical Federal Theology or Westminster Calvinism, attested by Trueman’s explication of the Covenant of Works, is that it collapses God into creation, by making a Covenant of Works shaped and predicated by creation, which in the Incarnation of God in Christ ends up determining and shaping how God must act in Christ for the world. This move, then, places a rupture into God’s life between the Son and the Father, such that the Son either becomes simply an organ and instrument of the Father (i.e. God), by which God accomplishes His purposes for the elect in salvation (i.e. He purchases them under the conditions laid out by the Covenant of Works–which is subsequent to creation instead of how it should be, subsequent to God’s act in creation from His own Triune life of love and grace-act), or the Son has always been subordinate (by a unity-of-will theology V. a unity-of-being theology) to the Father, and thus a creation of God himself (Arianism), or both (if not more). This is what makes Federal Theology, given shape by its logico-causal deductive schemata, imposed back upon a God-world relation as it does, most insidious to me. I.e. What it does to God’s own life. If a system of theology muddles God’s life in a way, and towards an end, that is dis-coordinate to who God has revealed Himself to be (as Triune plenitude); then even if said theology is touted as being pastorally rich and even called post Reformed orthodox, then I think we should quickly move away from such theology. In our moving away, we should, though, at least be attendant to any categories or emphases that may indeed (if only incidentally so) help to support a burgeoning grammar towards growing in the grace and knowledge of Jesus Christ (even if said grammar needs to be recasted and reified by a new and more orthodox theological framework and conceptuality–i.e. like Barth’s reification of the classic language of election and reprobation).
I hope this re-write has helped clarify further where I am coming from, and why, in the end I really do find Federal theology as insidious as I do. It is because of God. I also hope that you were able to see, in my re-write, how I still am open and hopeful about still being able to learn things from Federal theology; even if my mode is critical, and in a posture that believes that there is a better framework wherein classic Federal language can be better situated and utilized, and even marginalized by God’s Self-revelation in Jesus Christ.
 Carl R. Trueman, “Atonement and the Covenant of Redemption: John Owen On The Nature of Christ’s Satisfication” in From Heaven He Came and Sought Her, eds. David Gibson and Johnathan Gibson (Wheaton, IL: Crossway, 2013), 216-17.