Lotharian legend

[1] Due to the lack of a tangible explanation why the Corpus Iuris Civilis was the applicable law, different theories were developed during the Late Middle Ages and the beginning of the early modern period to justify its use.

[3] The authorship of the Chronica Carionis is, however, disputed and today the German Lutheran reformer and theologian Philip Melanchthon is considered to be the author of at least parts of it.

Legal historian Guido Kisch [de] considered the possibility that the Chronicon Urspergensis of Burchard of Ursperg could be its origin because Ursperg's discussion of Irnerius also notes Irnerius' patroness Matilda of Tuscany, but he concedes that this is inconclusive, because the Chronicon does not contain any reference to the alleged imperial decree of Lothair III.

[1] But to return to our present task: for those who really consult the old documents, this story of Emperor Lothar obviously not only stands on weak feet, but is completely false.

[...] So, because until today no decree, no even slightly older evidence exist, that Lothar rejected the laws in force until then, putting only the Roman ones in their place, it is quite clear how unfounded this commonly spread assertion is.In lieu of an imperial decree Conring's explanation for the applicability of Roman law was that it had been gradually adopted by the courts without a clear commandment to do so.

Conring thereby established the modern consensus view of a gradual reception of the ius commune focusing on the fact that in legal education only Roman law was taught and thus trained lawyers had a natural inclination to apply it.