Protestants believe in a doctrine called, “forensic justification”. I’ll quote the Protestant definition from a Protestant source:
….justification, instead of being an efficient act changing the inward character of the sinner, is a declarative act, announcing and determining his relation to the Law and justice of God. (Charles Hodge, Justification Is a Forensic Act).
If we define forensic justification as a legal declaration by which God declares a person just and we leave it at that, we would have no dispute between Rome and Evangelicalism. Though Rome has an antipathy to the concept of forensic justification, this antipathy is directed against the Protestant view of it. (R.C. Sproul, Imputed Righteousness: The Evangelical Doctrine).
Forensic justification and conversion
If you noticed, in RC Sproul’s definition, he claimed that the Catholic Church denies this doctrine. He says, “though Rome has an antipathy to the concept of forensic justification”. This couldn’t be further from the truth.
What Protestants call “forensic” justification, the Catholic Church calls “conversion”. Conversion is the point at which we turn to God in faith and begin to please Him. Let me read the Catechism:
1989 The first work of the grace of the Holy Spirit is conversion, effecting justification in accordance with Jesus' proclamation at the beginning of the Gospel: "Repent, for the kingdom of heaven is at hand." Moved by grace, man turns toward God and away from sin, thus accepting forgiveness and righteousness from on high. "Justification is not only the remission of sins, but also the sanctification and renewal of the interior man.
It is at this point that we become friends of God, but are not yet born again of the Spirit and therefore, not yet His Children. People (Catechumens) undergoing the Rite of Christian Initiaiton for Adults (RCIA) are, it can be assumed, forensically justified. They have repented of their sins and their sins have been forgiven, but not washed away. They have turned to God but have not yet received the Washing of Regeneration, Baptism, which makes them Children of God.
1249 Catechumens "are already joined to the Church, they are already of the household of Christ, and are quite frequently already living a life of faith, hope, and charity."48 "With love and solicitude mother Church already embraces them as her own."
Catechumens can be said to be “forensically” justified
Although we don’t use this terminology, we know that God has declared them righteous when they complete RCIA because they will be permitted to undergo Baptism. At that point, they will no longer simply be “forensically” justified. But they will be thoroughly washed of all their sins and become New Creatures in Christ.
1262 The different effects of Baptism are signified by the perceptible elements of the sacramental rite. Immersion in water symbolizes not only death and purification, but also regeneration and renewal. Thus the two principal effects are purification from sins and new birth in the Holy Spirit.65
1265 Baptism not only purifies from all sins, but also makes the neophyte "a new creature," an adopted son of God, who has become a "partaker of the divine nature,"69 member of Christ and co-heir with him,70 and a temple of the Holy Spirit.71
So, what is the beef between Catholic and Protestant on justification?
The main problem, in my opinion, is that the Protestant understanding of justification does not go beyond “forensic”. In other words, they don’t believe that they are changed inwardly. They claim to become new creatures, but they will deny with their last breath, that any real change occurs to the man. They simply believe they are covered over.
Whereas, the Catholic process of justification recognizes that men are declared righteous “forensically” when they begin to have faith in God and start to live a Christian lifestyle. At a certain point, they request Baptism and will be washed of all their sins by the Holy Spirit. Thus perfecting but not completing the process of justification which began when God initially called them to convert.