Objection 1. It would seem that the judicial precepts were not those which directed man in his relations to his neighbor. For judicial precepts take their name from "judgment." But there are many things that direct man as to his neighbor, which are not subordinate to judgment. Therefore the judicial precepts were not those which directed man in his relations to his neighbor.
Objection 2. Further, the judicial precepts are distinct from the moral precepts, as stated above (Question 99, Article 4). But there are many moral precepts which direct man as to his neighbor: as is evidently the case with the seven precepts of the second table. Therefore the judicial precepts are not so called from directing man as to his neighbor.
Objection 3. Further, as the ceremonial precepts relate to God, so do the judicial precepts relate to one's neighbor, as stated above (99, 4; 101, 1). But among the ceremonial precepts there are some which concern man himself, such as observances in matter of food and apparel, of which we have already spoken (102, 6, ad 1,6). Therefore the judicial precepts are not so called from directing man as to his neighbor.
On the contrary, It is reckoned (Ezekiel 18:8) among other works of a good and just man, that "he hath executed true judgment between man and man." But judicial precepts are so called from "judgment." Therefore it seems that the judicial precepts were those which directed the relations between man and man.
I answer that, As is evident from what we have stated above (95, 2; 99, 4), in every law, some precepts derive their binding force from the dictate of reason itself, because natural reason dictates that something ought to be done or to be avoided. These are called "moral" precepts: since human morals are based on reason. At the same time there are other precepts which derive their binding force, not from the very dictate of reason (because, considered in themselves, they do not imply an obligation of something due or undue); but from some institution, Divine or human: and such are certain determinations of the moral precepts. When therefore the moral precepts are fixed by Divine institution in matters relating to man's subordination to God, they are called "ceremonial" precepts: but when they refer to man's relations to other men, they are called "judicial" precepts. Hence there are two conditions attached to the judicial precepts: viz. first, that they refer to man's relations to other men; secondly, that they derive their binding force not from reason alone, but in virtue of their institution.
Reply to Objection 1. Judgments emanate through the official pronouncement of certain men who are at the head of affairs, and in whom the judicial power is vested. Now it belongs to those who are at the head of affairs to regulate not only litigious matters, but also voluntary contracts which are concluded between man and man, and whatever matters concern the community at large and the government thereof. Consequently the judicial precepts are not only those which concern actions at law; but also all those that are directed to the ordering of one man in relation to another, which ordering is subject to the direction of the sovereign as supreme judge.
Reply to Objection 2. This argument holds in respect of those precepts which direct man in his relations to his neighbor, and derive their binding force from the mere dictate of reason.
Reply to Objection 3. Even in those precepts which direct us to God, some are moral precepts, which the reason itself dictates when it is quickened by faith; such as that God is to be loved and worshipped. There are also ceremonial precepts, which have no binding force except in virtue of their Divine institution. Now God is concerned not only with the sacrifices that are offered to Him, but also with whatever relates to the fitness of those who offer sacrifices to Him and worship Him. Because men are ordained to God as to their end; wherefore it concerns God and, consequently, is a matter of ceremonial precept, that man should show some fitness for the divine worship. On the other hand, man is not ordained to his neighbor as to his end, so as to need to be disposed in himself with regard to his neighbor, for such is the relationship of a slave to his master, since a slave "is his master's in all that he is," as the Philosopher says (Polit. i, 2). Hence there are no judicial precepts ordaining man in himself; all such precepts are moral: because the reason, which is the principal in moral matters, holds the same position, in man, with regard to things that concern him, as a prince or judge holds in the state. Nevertheless we must take note that, since the relations of man to his neighbor are more subject to reason than the relations of man to God, there are more precepts whereby man is directed in his relations to his neighbor, than whereby he is directed to God. For the same reason there had to be more ceremonial than judicial precepts in the Law.
Source: Summa Theologica (New Advent)