CH-BTH-01 — Jus sanguinis ao nascer (BüG art.º 1)

1. Legitimate child of a married Swiss parent (either parent): Child born to a married couple where at least one parent holds Swiss citizenship at time of birth acquires Swiss citizenship automatically.
2. Child of an unmarried Swiss mother: Child born to an unmarried Swiss-citizen mother acquires Swiss citizenship automatically.
3. Child of an unmarried Swiss father: Acquisition is conditioned on paternity being legally established before the child turns 22 (Art 1(2) BüG); if established, acquisition is retroactive to birth.
4. No residency requirement: Birth may occur inside or outside Switzerland. Swiss citizenship is global-transmission.
5. Art 7 Verwirkung — age-25 retention requirement: A dual-national born abroad to a Swiss parent who is themselves born abroad must affirmatively register retention (Beibehaltung) before age 25, or apply for Wiedereinbürgerung. This is the only automatic-loss mechanism for birth-acquisition (see CH-OPSC-03, CH-RST-01).

Historical cohorts requiring separate analysis:

• Pre-1985 maternal-line: Under BüG 1952, children born before 1985 to Swiss mothers and foreign fathers did not automatically acquire Swiss citizenship unless the father acknowledged paternity or mother was unmarried. The 1985 reform (Bundesgesetz vom 23. März 1990 — in-force 1992-01-01) granted gender-equal transmission but did NOT retroactively confer citizenship on pre-1985 cohort (see CH-HIS-01, CH-DSC-01 for transitional treatment).
• Pre-1992 single-nationality era: If the Swiss parent naturalized in another country before 1992, they may have lost their Swiss citizenship under the old single-nationality regime (Bundesgesetz 1990-03-23 in-force 1992-01-01). In that case their child would not have acquired Swiss citizenship at birth.

Acquisition at birth is automatic (ex lege). The administrative acts are declaratory, not constitutive:

1. Birth registration — Child registered in Zivilstandsregister (civil register) at Swiss representation (consulate) for births abroad, or at cantonal civil registration office for births in Switzerland.
2. Heimatort entry — The transmitting Swiss parent's Heimatort is co-transmitted and entered in the register pursuant to Art 2 BüG.
3. Swiss passport application (optional but typical) — Application filed at Swiss representation (abroad) or cantonal passport office (in CH). Documents required: birth certificate, Swiss parent's passport, parents' marriage certificate (if applicable) or paternity acknowledgment document.
4. Art 7 Verwirkung registration (for abroad-born dual nationals) — If the child is born abroad and is a dual national, they must register before age 25. Registration is made at the consulate (Auslandschweizerregister, ASG Art 11) or by written declaration to SEM. Failure to register results in automatic loss at age 25.

• Citizenship acquisition: No fee (ex lege, automatic).
• Swiss passport (child under 18): CHF 35 (5-year validity) per GKGV SR 191.112.
• Swiss passport (adult): CHF 135 (10-year validity).
• Consular service fee for civil registration abroad: Varies by consulate; typically CHF 20-100.