It was the Emperor who was at the top position of the organization of government, according to the ritsuryo codes, it was the source of regent and chancellor's authority to act as Emperor or to support the emperor.
あくまで律令官制の最高位に君臨するのは天皇であり、その天皇を代行・補佐することが、摂関の権力の源泉となっていた。