About offshore delivery of demolition ship

Report from 　NIPPON SALVAGE ( NSC) MR Motoi
1, NSC Tugboat hands over the demolition ship to Korea by OPL.
2. NSC tugboat will not enter Korea.
3, NSC Salvage's ship will return immediately.

Our shipping agency / customs agency responds that this is an illegal act.
NSC MR Motoi is claiming to be legal.
I understand it is illegal as long as I research it in Japan.
I want to know whether this is illegal or legal.
Is it possible for you to carry out customs clearance procedures and vessel agency procedures for this demolition ship if it is legal?