a person similarly situated as A managed to return to Thailand and naturalized as a Thai national by fulfilling the abovementioned condition. However, there is no guarantee that A would acquire Thai nationality (even if return was possible) as the naturalization depends on the Thai government’s discretion. (3) Japan Application for naturalization is a possible measure to acquire Japanese nationality. However, even if A applies for naturalization, it is likely that the application would not be granted considering the facts that A has been convicted for illegal entry, A’s financial situation is not necessarily stable, and A does not read or write Japanese language. 3. Administrative response by Japan Japan’s response for many years had been to arrest Vietnamese refugees from Thailand as illegal entrants or stayers, grant provisional release after detaining them for a long term, and subsequently leave them as they were (under provisional release), being unable to forcibly remove them from Japan. Some have previously been detained for more than 2.5 years. However, after A won the litigation, Vietnamese refugees from Thailand similarly situated as A started to be granted special permission to stay along with long-term residency permits. It appears that the policy within the Immigration Bureau, Ministry of Justice has shifted. As a result, it has become possible for the above individuals to legally work and obtain national health insurance, and their living conditions in Japan have drastically been improved. They have also been issued a re-entry permits (ICRRA Article 26(2)) in lieu of a passports, and they have become able to visit Thailand on a short-term basis as “foreigners”. The attorney who represented A in his or her suit states that she is aware of at least 30 second-generation refugees from Thailand who are in a similar situation as A. The “Nationality/area of origin” column of the foreigner residency card for these 30 persons carries either “stateless” or “Vietnam”. As far as the author (an attorney) is aware, apart from these 30 persons, there are at least five persons who arrived in Japan from Thailand who nevertheless do not possess Thai nationality. It can be said that these persons are likely to be stateless due to not being considered nationals by any State under the operation of its law, including because they have difficulties establishing the facts based on which an assessment of nationality can be made. 4. Possible size of Category I (1) Unique nature of the category This sample case was about a person who was unable to have him or herself registered with the authorities of the country with which he had a relevant link (Vietnam) while in the country of birth, as the official documents containing his parents’ identity information 113