According to Delmaire 2005: 124 the date given by the text, that is 21 October 319, should be corrected as 21 October 313 (so the third, and not the fifth, consulship of Constantine and Licinius, and of Licinius Augustus, and not of Licinius Caesar). Delmaire assumes that Rufinus Octavianus (as corrector Lucaniae et Bruttiorum in CTh VII.22.1 (313) and I.16.1 (315)) to whom the law is addressed is the same as Octavianus who is comes Hispaniarum 316-317 (mentioned in CTh IX.1.1 and XII.1.4) and therefore the law must be earlier than 316. Delmaire accepts the correction of Seeck that the date should be read as CONSTANTINO A. III ET LICINIO III CONS.
For the arguments against the identification of Rufinus Octavianus with Octavianus comes Hispaniarum see Wiewiorowski 2006.