How has the Roman Catholic Church understood this great and glorious doctrine of justification? The Catholic Catechism says many things that at first glance appear copacetic with what I have argued thus far. It teaches that the Holy Spirit graciously converts the sinner, “effecting justification (CCC 1989)” wherein, “moved by grace, man turns toward God and away from sin, thus accepting forgiveness and righteousness from on high(CCC 1989).” The defect and decay of Rome’s doctrine of justification is in some respects subtle and misleading.
While on the one hand affirming the grace of the Spirit as the agent of justification, they on the other hand, insert baptism as the “sacrament of faith” through which, “justification is conferred (CCC 1992).” Elsewhere the Catholic Cathichsm asserts, “The grace of the Holy Spirit has the power to justify us, that is, to cleanse us from our sins and to communicate to us “the righteousness of God through faith in Jesus Christ” and through Baptism (CCC 1987),” which, “[imparts] the life of Christ's grace (CCC 405).” “By virtue of our Baptism,” Rome argues, “the first sacrament of the faith, the Holy Spirit in the Church communicates to us, intimately and personally, the life that originates in the Father and is offered to us in the Son. Baptism gives us the grace of new birth in God the Father, through his Son, in the Holy Spirit (CCC 683).” In short, the means by which Justification is applied to the believer is not the free and gracious work of the Holy Spirit, but the mechanical operation of the sacrament of baptism. ex opere operato (out of operation, operating). How then can justification be wrought “through the power of the Holy Spirit (CCC 1988)” when it is mechanistically activated by baptism?
Since the Council of Trent which was called to address Protestant “heresies,” Rome has rejected the doctrine of justification by faith alone, requiring human cooperation and preparation for grace: “ If any one saith, that by faith alone the impious is justiﬁed; in such wise as to mean, that nothing else is required to co-operate in order to the obtaining the grace of Justiﬁcation, and that it is not in any way necessary, that he be prepared and disposed by the movement of his own will; let him be anathema.” They insist instead that human effort, striving, and works are truly the means by which someone comes to justification and remains in a state of grace. Far from a once and for all gracious declaration of “innocent,” justification, according to the Catholic schema, is declared at the end of a believers life, when they, “through the observance of the commandments of God and of the Church, faith co-operating with good works, increase in that righteousness which they have received through the grace of Christ and are still further justified.” So what must man do to be saved? According to your system he must prepare himself for grace and then bear meritorious fruit from the seed of righteousness infused into his soul. In short, one stays in the covenant the same way they entered into it, their own effort. How then is this a Covenant of Grace and not of Works?
There is a dangerous merging of justification and sanctification within the Catholic scheme that blurs the annihilates the distinction between the finished work of Christ and the ongoing work of progressive growth in grace, “Justification is not only the remission of sins, but also the sanctification and renewal of the interior man (CCC 1989).” Elsewhere it states, “Justification establishes cooperation between God’s grace and man’s freedom. On man’s part it is expressed by the assent of faith to the Word of God...(CCC 1993).” Don’t you see the horrid error of conflating the finished work of Christ with the imperfect, progressive, nonmeritorious works of man?
Thanks be to God that nothing could be further from the truth! Since justification is completely and totally an act of God’s free grace in which I am constituted and declared righteous and adopted into the family of God, my standing before him is not determined by my performance or cooperation but upon the finished work of Jesus Christ alone. He lived the sinless life that I could have never lived to keep the law that I was commanded to uphold and he died the death that my sins deserved! His righteousness is imputed to me and received by faith while my record of violations of the law of God is imputed to him as my substitute, my spotless lamb. Thus, on the cross the transfer was complete and the wrathful justice of God was satisfied, “For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God (2 Cor. 5:21).” They hymn writer said it well, “I owed a debt I could not pay and he paid a debt he did not owe.”
 Nampon Rev., Catholic Doctrine, 301.
 J V. Fesko, Justification: Understanding the Classic Reformed Doctrine (Phillipsburg, N.J.: P & R Pub., 2008), 353-54.