Reservation-failure retroactive loss (foreign-born duals)
Citizenship in Japan
- Eligibility
- A Japanese acquiring a foreign nationality at birth while born ABROAD (国外) retroactively loses Japanese nationality unless a nationality reservation is filed within 3 months of birth (Art.12 + Family Register Act Art.104). Constitutionality upheld SC 3rd Petty Bench 2015-03-10.
- Renunciation
- Not required
Timeline
- The Art. 12 nationality-reservation (国籍留保) intent must be expressed within 3 months of the date of birth, filed together with the birth notification, by a person entitled to give the birth notification (Family Register Act Art. 104(1)-(2)); a 14-day extension applies where the deadline was missed for reasons not attributable to the filer (Art. 104(3)).
Legal basis
Primary legal authorities: Nationality Act Art.12, Family Register Act Art.104, SC 2015-03-10 平成25(行ツ)230. Status: Operative (—present). Administering authority: Ministry of Justice (法務省), Civil Affairs Bureau, via the Legal Affairs Bureaus (法務局); consular missions (外務省) for notifications/applications filed abroad. A Japanese acquiring a foreign nationality at birth while born ABROAD (国外) retroactively loses Japanese nationality unless a nationality reservation is filed within 3 months of birth (Art.12 + Family Register Act Art.104). Constitutionality upheld SC 3rd Petty Bench 2015-03-10.
Competent authority
- The Supreme Court (3rd Petty Bench, 2015-03-10, docket 平成25(行ツ)230, 民集69巻2号265頁) upheld the constitutionality of Art. 12 retroactive loss against challenges under Constitution Arts. 13 and 14(1), holding the reservation mechanism a reasonable means tied to genuine connection and avoidance of formalistic nationality.
Example scenarios
Yuki acquired Japanese nationality at birth under Art. 2(i) (father Japanese) but then lost it retroactively under Art. 12: she was born abroad (Canada), acquired Canadian nationality at birth, and no reservation was filed within 3 months. She is therefore not currently a Japanese national (loss was retroactive to birth). Art. 17(1) reacquisition is available: she is under 18 (she is 14), and she has a domicile in Japan (Tokyo for 2 years). She may reacquire Japanese nationality by notification to the Minister of Justice. The notification is filed in person at the Legal Affairs Bureau. Reacquisition takes effect at the time of the notification (Art. 17(3)). After reacquisition, she files a koseki entry notification within 1 month (Family Register Act Art. 102). Since she is under 15, her father (as statutory agent, Art. 18) makes the notification on her behalf. This must happen BEFORE she turns 18.
Art. 12 applied: born abroad + Canadian nationality at birth + no reservation → retroactive loss | Art. 17(1) reacquisition available: under 18 + Japanese domicile | Notification effective at filing (Art. 17(3)) | Under-15: father as statutory agent (Art. 18) | Window closes at age 18 — must act before then
Informational summary compiled from primary legal sources — not legal advice. Citizenship law changes; verify with the competent authority before acting. Last verified 2026-06-21.
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