"For this, you need to obtain an IPv6 address from your ISP. Technically this could be a
/128
prefix (exactly one IPv6 address), but according to regulation it needs to be at least a/64
prefix."
from the OpenWRT Wiki
To what regulations are they referring? (So that if I need to defend myself when the time comes, I'll be able to point to something)
It likely refers to the RFC 6177.