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Sources of Roman Law IUS NON SCRIPTUM - the custom question
Twelve Tables are the first example of actual written law. With the exception of Royal Decrees (which did not quite resemble a lex), law was undeclared in the archaic period. o Watson says that royal legislation was not impossible, but was unlikely. o Logical conclusion is that it was determined by custom i.e. accepted practices of what 'the done thing' was. o The question is whether these practices could be considered legally binding.
Justinian recognises the existence of ius non scriptum at I.2.3: "like the Greeks, our law is both written and unwritten". Justinian sees the law as binding - I.2.9 - but it is possible that this understanding of its binding nature is a post-Classical one. o Justinian points out at D.188.8.131.52 that if statute is to be binding only because it was approved by the people, so too should custom be binding because it has been similarly approved but without the formal legislative process. o Bear in mind that Justinian lived in a time where there was a vast body of written law that was deemed excellent.
Gaius makes no mention of unwritten law and its binding nature. o It may be argued that during the Classical period where Imperial power was rising, it would have been improper to suggest that it law could be merely customary. o MacCormack argues that custom was not a source of law, but that it provided a historical setting for the law to develop.
There is debate over whether a custom could abrogate an opposing lex. Justinian seems to suggest it could in D.184.108.40.206, but later writings disagree. It is highly improbable that custom could take precedence over lex.
The jurists - responsa prudentium (see below). Through the ius respondendi, the jurists had a lot of legal power, although not official. o Thomas argues that the jurists interpreted 'the law' in a manner entirely consistent with custom. The interpretation and its legitimisation through magistrates etc. turned custom into law.
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