I just came across this very engaging op/ed at The Japan Times [edited for length and highlighted for my emphasis]:
Collective self-defense and collective security: what the differences mean for Japan
By CRAIG MARTIN
Thursday, Aug. 30, 2007
PHILADELPHIA – As the debate in Japan heats up over whether and how to amend Article 9 of the Constitution, the terms “collective self-defense” and “collective security” are often used in the same breath, almost as though they were synonymous. Often the terms are avoided altogether.
The terms “collective self-defense” and “collective security,” however, each have a very precise meaning under international law, and the amendment of Article 9 to allow Japan to engage in either one would have very specific and different consequences. [...] A more precise use of these terms ought to preclude the government from hiding behind such woolly terms as “international peace cooperation activities.”