Under Imperial House Law during the Meiji period, it was not allowed for subjects who once left the Imperial Family to return to the Imperial Family since it was considered to 'confuse the moral of sovereignty and subjects,' but there were some examples where the Emperor's family changed to the Imperial Family during the Kamakura period.
なお、明治の皇室典範は臣籍から皇籍への復帰を「君臣の分を乱すもの」として認めていないが、鎌倉時代まで遡ると王氏から皇族への復帰の例は存在する。