US <-> Europe <-> Japan

I found 7 posts with the questions:
Can i play Europe games from USA,
Can i play USA games from Europe...

Here explain:
Between USA and Europe you can switch if you want... its not illegal

BUT!

from USA to Japan
or from Europe to Japan, Korea, China

ITS MOSTLY ILLEGAL!

Why?
Cuz of the KSSN or JKA you need it for Registration... its not allowed to make false KSSN / JKA by Generator
is ILLEGAL!