I believe many of trade practitioner face language barrier in looking into Japanese trade related laws and regulations. Yes, in reality, English translation is not always available and difficult to find it.
For those who need English translation of Japanese law, here's some useful information.
1) Government Web site http://www.cas.go.jp/jp/seisaku/hourei/data2.html
This site is very useful. Although the translation is unofficial one, it is permitted to cite, reproduce or reprint as needed. This site doesn't cover all Japanese law, e.g. 薬事法Pharmaceutical Affairs Law is not available, but they continue to add new translation regularly.
Please be noted, the export control related laws are available, but not reflecting the latest one.
For example, FEFTL (Foreign Exchange and Foreign Trade Act) translation is in 2005, and Export Trade Control Order is in 2006. Both of them were slightly modified in 2007 and 2008.
2) Book published by Japan Tariff Association http://www.kanzei.or.jp/book/publish03.htm
Customs related law is not available in above government web site.
Instead, Japan Tariff Association sell English translation book of Customs related law.
4-88895-255-8 英文関税法規集 B5/546 Price: JPY18,900.-
Customs Law http://www.kanzei.or.jp/book/pdf/tariff_law_english.pdf
3) Eibun-Horei-Sha, Inc. http://www.ehs.or.jp/index_en.html
They sell English translation of law books for many fields. However in trade related law, the content is too old for some books. For example, Export Trade Control Order with Concomitant Notification is in 1991 edition! They sell Export Inspection Law, 1990 edition but this law was abolished in 1997.