Gratian, De legibus, Distinctiones 1-20 Structure of Gratian III:

Distinctiones 1-101 (Pars Prima)

Causae 1-36 (Pars Secunda)

De penitentia (C.33 q.3)

De consecratione

Humanum genus duobus regitur, naturali uidelicet iure et moribus. Ius naturae est, quod in lege et euangelio continetur, quo quisque iubetur alii facere, quod sibi uult fieri, et prohibetur alii inferre, quod sibi nolit fieri. Unde Christus in euangelio: "Omnia quecunque uultis ut faciant uobis homines, et uos eadem facite illis. Haec est enim lex et prophetae. [Matthew 7:12, cf. Luke 6:31]"

Dictum before chapter 1, Distinctio 1 (D.1 d.a.c.1): 

The Human Race is ruled by two things:  namely, natural law and long standing custom (mos).  Natural law is what is contained in the law and the Gospel.  By it, each person is commanded to do to others what he wants done to himself and is prohibited from inflicting on others what he does not want done to himself.

Reading: Pennington, Lex naturalis and Ius naturale

Link to the Manuscripts in the Cologne Cathedral Chapter Library

Cologne, Dombibl. 127, fol. 9r

Cologne, Dombibl. 127, fol. 9v

Cologne Dombibl.127, 10r

Cologne, Dombibl.127, 10v

 

Cologne, Dombibl. 127, 13v

Cologne, Dombibl. 127, 14r

Roman Law Source of Gratian's First Dictum

D.1 c.1 Fas et ius

D.1 c.5 Lex et ratio

Ratione lex constat (Law is confirmed through reason)

D.1 c.7:  Ius naturale: Omnium una libertas

Roman law jurists use canon law

D.4 dictum after c.3:  

 <Gratianus>. Leges instituuntur, cum promulgantur, firmantur, cum moribus utentium approbantur. Sicut enim moribus utentium in contrarium nonnullae leges hodie abrogatae sunt, ita moribus utentium ipsae leges confirmantur. (Laws are instituted when they are promulgated;  they are confirmed when they have been approved by the long standing custom of those who observe themSome laws have have been abrogated by the long standing custom of those who have acted contrary to them, because laws are confirmed by the long standing custom of those who observe them).

The Canonists reflect upon Ius:

Gratian's Hierarchy of Laws and the Role of Consent

Huguccio:  Ius and Reason

Laurentius Hispanus, Pope Innocent III:  Quanto personam and Pro ratione voluntas

D.12 c.6:  Laws abrogate or derogate custom; The Editing of Gratian

D. 19 and D.20: The Authority of Papal Decretals