It is prescribed in the Kushiki-ryo (law on state documentary forms) in the Taiho Code, and it says that ketsuji should be used when words such as the following appear: 'a grand shrine,' 'the Imperial tomb for a certain emperor,' 'the son of Heaven', 'an Imperial carriage,' 'shosho,' 'chokushi,' 'an Imperial edict and Imperial order,' 'an emperor's cultivating his or her virtue,' 'Emperor's blessings,' 'Emperor's grace,' 'Emperor's words,' 'Your Imperial Majesty,' 'the Emperor's residence,' 'an Empress,' 'the Imperial Court,' 'the Crown Prince,' 'His or Her Imperial Highness.'
大宝律令公式令に定めがあり、具体的には「大社」「○○陵」「乗輿」「車駕」「詔書」「勅旨」「明詔」「聖化」「天恩」「慈恩」「慈旨」「御（至尊）」「闕庭」「中宮」「朝廷」「春宮」「殿下」などの語に対して用いるべきとある。