Bruns, FIRA and Girard include selections (see below).
The Codex Gregorianus, imperial statutes from the time of Hadrian (117-138 AD) – c. 291 AD, and Codex Hermogenianus, which supplements the Gregorianus, are included in t.3 of the Collectio (see below).
The Codex Theodosianus comprises Imperial statutes from the time of Constantine the Great (312 AD) to 438 AD.
For Gaius, Ulpian and Paulus see FIRA, Girard and Collectio t.1 and t. 2.
Fragmenta Vaticana, which includes both imperial enactments and abstracts from the writings of Papinian, Ulpian and Paulus are reproduced in Collectio t.3, FIRA, Girard and Huschke.