Suggested subject searches in SOLO:
Roman law sources
Roman law history
Roman law interpretation and construction history
Roman law reception [followed by modern geographic area eg Spain]
as well as the specific names
eg Codex Hermogenianus
After Caracalla granted Roman citizenship to all inhabitants of the Roman Empire (212 AD), ius civile was available to all.
What is not clear is how much in practice local, indigenous legal culture and practices survived.
By 3rd and 4th century AD power was shifting from the central Roman authorities to the leaders of the foederati (allies) became the rulers of the provinces of old Empire.
The leaders of these Germanic tribes - the Ostrogoths, Visigoths, Franks, and Burgundians - rather than being out and out vandals or barbarians in the loose modern sense, saw the advantages of having a written law - and ordered paraphrases and modifications of Roman law to be written down for their territories.
Terms such as (Roman) Vulgar law and "barbarized Roman law" have been used to designate the resulting documents - but as both now sound pejorative, modern practice uses names reflecting the tribal/geographic/royal origins/attributions eg Salic Law, Breviary of Alaric etc. This can lead to complications the Lombardic laws or the Edict of King Rothari (AD643) and King Liutprand's extensions. Certainly when embarking on literature searches it would be wise to use the older terms as well - such as Roman vulgar law - to ensure you do not miss some classic commentary.
When Roman law was rediscovered by eleventh century (and later) scholars, the version recorded by the rulers of the Eastern Roman Empire, Justinian in particular, became central to their basic understanding of its principles and application.
426 Law of Citations (Lex Citandi)
438 Codex Theodosianus
post-Theodosian Novels (Novellae posttheodosianae).
529 Codex Justinianus
533 Digesta or Pandectae
534 Codex Repetitae Praelectionis (2nd edition of CJ)
(after 534) Novellæ constitutiones