Rather bad reporting in that article. Percocet (or maybe Oxycontin) is used for much more than cancer and it is certainly not "stronger than morphine."
Interesting that the article, which may or may not also be misinformed here, said oxycodone is illegal in Japan "without a prescription." I wonder if that means it can be prescribed in Japan and/or if it could be brought in by a patient with a proper prescription.
In any event, the real case here involves an attempt to import the meds through deception, in a package labeled "necklace." That is illegal anywhere in the developed world.