They are considered to be "by far the most influential elementary-systematic presentation of Roman private law in late antiquity, the Middle Ages and modern times".

[1] The original Latin text with an English translation by Francis De Zulueta covers around 300 pages (with critical notes).

[5] An almost complete version of the Institutes was discovered by Barthold Georg Niebuhr in 1816 in the form of a palimpsest in Verona (Austrian Empire, now in Italy).

Niebuhr had just accepted a post as Prussian ambassador to the Papal States, when he was dispatched to negotiate a concordat with the Catholic Church.

[10] Savigny publicized the discovery of the manuscript and his conjecture, that Gaius' Institutes had been found, in the 1817 volume of his Zeitschrift für geschichtliche Rechtswissenschaft [de] (Journal of Historical Jurisprudence).

[11] Niebuhr vermuthet auf Ulpian; ich bin [...] geneigt, vielmehr die Institutionen des Gajus zu erwarten, so daß unser erstes Fragment ein einzelnes nicht rescribiertes Blatt derselben Handschrift wäre.

Niebuhr assumes Ulpian; [...] I am inclined to rather expect the Institutions of Gajus, so that our first fragment would be a single unrescribed page of the same manuscript.

[18] The work of Gaius has also been indirectly handed down to modern times,[19] as it was frequently used as a model for various legal writings during the 5th and 6th centuries.

[24] In Der kleine Pauly, they are described by the German legal scholar Theo Mayer-Maly [de] as "by far the most influential elementary-systematic presentation of Roman private law in late antiquity, the Middle Ages and modern times".

[26] Theo Mayer-Maly argued that Gaius' legal thinking is "much closer to the dogmatic tradition of continental [European] jurisprudence (i.e. the striving for systems, the effort to form concepts and to classify, and the tendency towards abstraction) than the method of any other ancient jurist".

[27] Gaius writes in translation of Edward Poste: § 1 Omnes populi qui legibus et moribus reguntur, partim suo proprio, partim communi omnium hominum iure utuntur; nam quod quisque populus ipse sibi ius constituit, id ipsius proprium est uocaturque ius ciuile, quasi ius proprium ciuitatis; quod uero naturalis ratio inter omnes homines constituit, id apud omnes populos peraeque custoditur uocaturque ius gentium, quasi quo iure omnes gentes utuntur.

[24] This classification scheme, probably borrowed from the Hellenistic textbook pattern,[24] replaced and leveled previous structures and became a basic model followed by many modern civil law systems.

Furthermore, the structure of the Institutes was a model for the Castilian Siete Partidas, the French Code Napoléon and even the Corpus Juris Canonici.

[33] Multiple editions of the Institutes have been published since the discovery of the Codex Veronensis, beginning with the editio princeps of Johann Friedrich Ludwig Göschen [de] (Berlin, 1820).