Objection 1. It would seem that the debt of punishment is not an effect of sin. For that which is accidentally related to a thing, does not seem to be its proper effect. Now the debt of punishment is accidentally related to sin, for it is beside the intention of the sinner. Therefore the debt of punishment is not an effect of sin.
Objection 2. Further, evil is not the cause of good. But punishment is good, since it is just, and is from God. Therefore it is not an effect of sin, which is evil.
Objection 3. Further, Augustine says (Confess. i) that "every inordinate affection is its own punishment." But punishment does not incur a further debt of punishment, because then it would go on indefinitely. Therefore sin does not incur the debt of punishment.
On the contrary, It is written (Romans 2:9): "Tribulation and anguish upon every soul of man that worketh evil." But to work evil is to sin. Therefore sin incurs a punishment which is signified by the words "tribulation and anguish."
I answer that, It has passed from natural things to human affairs that whenever one thing rises up against another, it suffers some detriment therefrom. For we observe in natural things that when one contrary supervenes, the other acts with greater energy, for which reason "hot water freezes more rapidly," as stated in Meteor. i, 12. Wherefore we find that the natural inclination of man is to repress those who rise up against him. Now it is evident that all things contained in an order, are, in a manner, one, in relation to the principle of that order. Consequently, whatever rises up against an order, is put down by that order or by the principle thereof. And because sin is an inordinate act, it is evident that whoever sins, commits an offense against an order: wherefore he is put down, in consequence, by that same order, which repression is punishment.
Accordingly, man can be punished with a threefold punishment corresponding to the three orders to which the human will is subject. In the first place a man's nature is subjected to the order of his own reason; secondly, it is subjected to the order of another man who governs him either in spiritual or in temporal matters, as a member either of the state or of the household; thirdly, it is subjected to the universal order of the Divine government. Now each of these orders is disturbed by sin, for the sinner acts against his reason, and against human and Divine law. Wherefore he incurs a threefold punishment; one, inflicted by himself, viz. remorse of conscience; another, inflicted by man; and a third, inflicted by God.
Reply to Objection 1. Punishment follows sin, inasmuch as this is an evil by reason of its being inordinate. Wherefore just as evil is accidental to the sinner's act, being beside his intention, so also is the debt of punishment.
Reply to Objection 2. Further, a just punishment may be inflicted either by God or by man: wherefore the punishment itself is the effect of sin, not directly but dispositively. Sin, however, makes man deserving of punishment, and that is an evil: for Dionysius says (Div. Nom. iv) that "punishment is not an evil, but to deserve punishment is." Consequently the debt of punishment is considered to be directly the effect of sin.
Reply to Objection 3. This punishment of the "inordinate affection" is due to sin as overturning the order of reason. Nevertheless sin incurs a further punishment, through disturbing the order of the Divine or human law.
Source: Summa Theologica (New Advent)