Objection 1. It would seem that the judicial precepts of the Old Law bind for ever. Because the judicial precepts relate to the virtue of justice: since a judgment is an execution of the virtue of justice. Now "justice is perpetual and immortal" (Wisdom 1:15). Therefore the judicial precepts bind for ever.
Objection 2. Further, Divine institutions are more enduring than human institutions. But the judicial precepts of human laws bind for ever. Therefore much more do the judicial precepts of the Divine Law.
Objection 3. Further, the Apostle says (Hebrews 7:18) that "there is a setting aside of the former commandment, because of the weakness and unprofitableness thereof." Now this is true of the ceremonial precept, which "could [Vulgate: 'can'] not, as to the conscience, make him perfect that serveth only in meats and in drinks, and divers washings and justices of the flesh," as the Apostle declares (Hebrews 9:9-10). On the other hand, the judicial precepts were useful and efficacious in respect of the purpose for which they were instituted, viz. to establish justice and equity among men. Therefore the judicial precepts of the Old Law are not set aside, but still retain their efficacy.
On the contrary, The Apostle says (Hebrews 7:12) that "the priesthood being translated it is necessary that a translation also be made of the Law." But the priesthood was transferred from Aaron to Christ. Therefore the entire Law was also transferred. Therefore the judicial precepts are no longer in force.
I answer that, The judicial precepts did not bind for ever, but were annulled by the coming of Christ: yet not in the same way as the ceremonial precepts. For the ceremonial precepts were annulled so far as to be not only "dead," but also deadly to those who observe them since the coming of Christ, especially since the promulgation of the Gospel. On the other hand, the judicial precepts are dead indeed, because they have no binding force: but they are not deadly. For if a sovereign were to order these judicial precepts to be observed in his kingdom, he would not sin: unless perchance they were observed, or ordered to be observed, as though they derived their binding force through being institutions of the Old Law: for it would be a deadly sin to intend to observe them thus.
The reason for this difference may be gathered from what has been said above (Article 2). For it has been stated that the ceremonial precepts are figurative primarily and in themselves, as being instituted chiefly for the purpose of foreshadowing the mysteries of Christ to come. On the other hand, the judicial precepts were not instituted that they might be figures, but that they might shape the state of that people who were directed to Christ. Consequently, when the state of that people changed with the coming of Christ, the judicial precepts lost their binding force: for the Law was a pedagogue, leading men to Christ, as stated in Galatians 3:24. Since, however, these judicial precepts are instituted, not for the purpose of being figures, but for the performance of certain deeds, the observance thereof is not prejudicial to the truth of faith. But the intention of observing them, as though one were bound by the Law, is prejudicial to the truth of faith: because it would follow that the former state of the people still lasts, and that Christ has not yet come.
Reply to Objection 1. The obligation of observing justice is indeed perpetual. But the determination of those things that are just, according to human or Divine institution, must needs be different, according to the different states of mankind.
Reply to Objection 2. The judicial precepts established by men retain their binding force for ever, so long as the state of government remains the same. But if the state or nation pass to another form of government, the laws must needs be changed. For democracy, which is government by the people, demands different laws from those of oligarchy, which is government by the rich, as the Philosopher shows (Polit. iv, 1). Consequently when the state of that people changed, the judicial precepts had to be changed also.
Reply to Objection 3. Those judicial precepts directed the people to justice and equity, in keeping with the demands of that state. But after the coming of Christ, there had to be a change in the state of that people, so that in Christ there was no distinction between Gentile and Jew, as there had been before. For this reason the judicial precepts needed to be changed also.
Source: Summa Theologica (New Advent)