As the reason, they explained that the word 'evil customs of the past' in shinkan (Imperial letter) issued at the same time as Charter Oath was not restricted to national isolation as well as expulsion of foreigners, and Takayoshi KIDO himself used the words 'old customs', 'evil customs of the past' and 'conventions' widely as meaning of 'feudalism to be conquered' or 'closed nature to be conquered', and even Toshimichi OKUBO severely criticized the same thing as 'evil customs of the past' mentioned by Kido for 'corrupt smell of old customes', in other word, though both Satsuma and Choshu provided overseas education secretly and were liberal domains led the movement of overthrowing the Shogunate, Okubo from Satsuma recognized more about dangerous feudalism as well as closed nature than Kido from Choshu, Okubo had to criticize more extreme because of internal affair regarding father and son of the lords of his domain and internal circumstances of his domain (The Teradaya Incident - Seinan War), moreover Tomomi IWAKURA also used just the same words 'the laws of Nature' as 'reason of nature' in other document, which meant totally different from international public law.
その理由として、御誓文と同時に出された宸翰に出てくる「旧来の陋習」の語がそもそも鎖国攘夷の意味に限定されていないこと、また木戸孝允自身が「打破すべき封建性」「打破すべき閉鎖性」の意味で「旧習」「旧来の陋習」「陋習」という言葉を広く使用していること、また、大久保利通でさえ木戸の「旧来の陋習」と同じ意味のことを「因循の腐臭」とより痛烈に批判していること、つまり、薩長いずれも密留学をさせ倒幕に立ち上がった開明的雄藩であったにもかかわらず長州の木戸より薩摩の大久保のほうが藩主父子・出身藩の内部事情などのためにより批判的にならざるを得ない危険な封建性・閉鎖性をより自覚していたということ（寺田屋事件～西南戦争）、更に、岩倉具視も他の文書で「天地の公道」という全く同じ言葉を万国公法とはおよそ次元の異なる「天然自然の条理というような意味」で用いていることなどが挙げられている。