Laws can be searched by keyword, by title, by number, by category, or by organization (institution).
I found Japanese Law Translation to be a very clear and well-organized website. Would love to hear how Japanese speakers find it.
I particularly liked the “Key Word in Context” function – you can see an example below.
Another potentially useful way of browsing the legislation, in my opinion, would be by “organization” – see below.
All of the translations contained in the “Japanese Law Translation Database System” are unofficial. Only the original Japanese texts of the laws and regulations have legal effect, and the translations are to be used solely as reference materials to aid in the understanding of Japanese laws and regulations.
Any data that the title of a law indicates to be a “Tentative translation” has not yet been proofread or corrected by a native English speaker or legal translation expert; this data may be revised in the future.
You might also be interested in this article retracing developments in Japanese law and describing available (paper-based) publications, by Colin P. A. Jones, a law professor living in Kyoto.