No other Regional Internet Registry currently has an inter-RIR ASN
transfer policy that would permit the transfer of ASNs between regions.
For context: In July 2013, the ARIN AC abandoned draft policy ARIN-2013-1 "Section 8.4 Inter-RIR Transfers of ASNs", because "The feedback from the community indicated that many people felt the policy was unnecessary as it would have no effect until/unless another RIR expresses interest in allowing Inter-RIR ASN transfers as well." - http://lists.arin.net/pipermail/arin-ppml/2013-July/027028.html
Obviously that is no longer true, now that APNIC has implemented an inter-RIR ASN transfer policy. Speaking as an individual active in the ARIN policy development process (and NOT on behalf of the AC), I would be happy to consider a new inter-RIR ASN transfer policy proposal if anyone thinks it would be useful.