Ryosei (systems based on ryo) (令制)
Ryosei is the systems based on ryo that refer to the administrative law of the Ritsuryo codes. In Japan, the systems based on Taiho Code and Yoro Ritsuryo Code, which were enacted and enforced in the eighth century, were regarded as Ryosei. For example, those government posts in the Ritsuryo codes, provinces as a unit of local administration (ryoseikoku), the format of documents and so on are mentioned.
Refer to the article on the ritsuryo system for further information.