Kyakushiki refers to laws and ordinances which were passed in complement to the Ritsuryo codes, or law codes which were the collections of those codes. Kyaku refers to laws and ordinances (auxiliary law) which were for the amendment and supplement of the Ritsuryo, and shiki (nori) were detailed enforcement regulations of the Ritsuryo.
Its application, however, differs among China, Japan and Korea. In contrast to China, where revision and enforcement were made to cover for the insufficiency of the Ritsuryo codes that were compiled simultaneously, Japan took the style of revising on a later day, all the laws and ordinances that were added in the forms of imperial edicts and Daijokanpu (official documents issued by Daijokan, Grand Council of State) after the compilation of the Ritsuryo codes. As for Kyaku, too, as opposed to China, where after the fall of the Tung dynasty, it had diminished into restrictive law which stated the qualifications for government officials, the share of Kyaku became high since not one new Ritsuryo code were made at all from the Yoro Ritsuryo code in Japan, and even laws and ordinances (for example, "konden einen shizai ho", the Law Permitting Permanent Ownership of Newly Cultivated Land) which denied the rules by the Ritsuryo codes were passed in the form of Kyaku. As a result, there were cases where shiki made detailed enforcement regulations of kyaku, and from the middle of the Heian period, although on surface, it was politics based on the Ritsuryo codes, it was actually 'kyaku shiki seiji' (politics based on amendments and enforcement regulations of the Ritsuryo). Also, in Korea, while accepting the Ritsuryo codes of the Tung dynasty, amendments were made by kyakushiki according to the conditions of the country.
Kyaku in the form of legal codes, was by and large written as the original text including sentences and dates of proclamation, and were arranged according to the government officials concerned. In addition, Shiki was used not only as the detailed enforcement regulations of the ryo which was the administrative law, but also as legal basis (including such as 'kebiishi shiki' that enacted the placement of kebiishi (officials with judicial and police powers)) which were placed after the enforcement of ryo to complete the formation of officials outside of the ryo codes. Furthermore, the type of regulation based on shiki includes "rei".