The Wikipedia code book definition that you provided is about codes that are concerned with encryption/deciphering (as in secret codes, etc.)

In your question, however, I believe that the word "code" in "code book" is about laws (to protect the people from inter-city violence, etc.)

WordWeb defines code as: A set of rules or principles or laws (especially written ones)

Here is a website with some information on “code book” (book of codes that relates to protecting the public, etc. (please read some of it if you have the time):

http://www.codebookcity.com/
Code books exist to protect the public, as well as private end-users. In liability suits, the "should have known" principle applies. If you are responsible for the design, management, or installation of a project, you are liable for code-covered issues.
Code books, however, often appear intimidating or even incomprehensible. Appearances can be deceiving. The following tips will help you understand how best to use code books.
Don't forget: code compliance is not optional. Ignorance of the codes is no excuse under the law


More about codes:
http://ja.wikipedia.org/wiki/法典
http://en.wikipedia.org/wiki/Code_(law).
http://dictionary.goo.ne.jp/dicindex/ej/COD/u/C/
code
[名]1 法典, 法律の集大成 the code of civil ［criminal］ procedure民事［刑事］訴訟法 the Code of Hammurabiハンムラビ法典.2 （行...

Anyway, I think a book of laws to refer to, follow, and abide by is the meaning of your "code book." :-)