Fukai-no-Joten/ Fukaijoten is said to be established by Emperor Tenchi for the first time, however, in "Nihonshoki" (Chronicles of Japan), there are only descriptions on legal amendment and no description on a newly instituted law is found.
不改常典は天智天皇が初め定めたと言われるのに、『日本書紀』が天智天皇の時代には、改定はあっても初めて定めた法が見えない。