log after the fact, and for the most
cases that will be fine.
Perhaps change the constraint to a 'notice of public objection' (or
some other wording) based on the idea that other members can observe
if any issues are apparent, and voice feedback prior to allocation.
as some loose text:
"When a member disposes of address space using this transfer policy,
and requests further IPv4 allocations from APNIC within 12 months. A
notice of public objection will be posted on the APNIC website for 1
month prior to any request being fulfilled."
This doesn't stop any _needed_ allocations from happening post
transfer (ie not inhibiting business), and further highlights who is
doing what and why so gives more transparency to the process.