Although attempts were made to demarcate the ryoseikoku provinces by boundaries based on domains conventionally ruled by Kuninomiyatsuko (local ruling families in ancient Japan) and gozoku, mountain ridges or rivers, the demarcation of the provinces could hardly come to a conclusion and it was not until the regime of Emperor Tenchi had began that the demarcation was finalized.
令制国は、旧来の国造・豪族の支配範囲や山稜・河川に沿って境界画定作業が行われたが、境界はなかなか定まらず、後の天智天皇の頃にようやく令制国が画定することとなった。