Dynamisches Zwölftafelrecht und statisches ius gentium. Inst. 2.1.41

Like other ancient laws the Twelve Tables required in case of sale for the acquisition of goods that the prize had been paid. This requirement could be replaced by the arrangement of a surety or even, without any replacement, be dropped, just as the seller wished. The requirement of payment was part of the law, the replacement by way of arrangement of a surety was the result of interpretation, the possibility of letting things drop, was a provision, which presumably goes back to Q.Mucius Scaevola. In this way Roman law gained, by jurisprudence, a higher level of quality, whereas other laws and the ius gentium, for lack of jurisprudence, remained unchanged. Developments like this one caused the maiores to separate ius civile from ius gentium.