Erwerb von Geburts wegen / jus sanguinis al nacer (BüG Art 1(1))

CH-BTH-01 is the principal mode of acquiring Swiss citizenship: acquisition von Geburt an (from birth) by jus sanguinis under Article 1 of the Buergerrechtsgesetz (BueG, SR 141.0, in force 2018-01-01). A child is Swiss from birth if its parents are married to each other and the father OR the mother is a Swiss citizen (Art 1(1)(a)), or if it is the child of a Swiss-citizen mother who is not married to the father (Art 1(1)(b)). Switzerland operates PURE jus sanguinis; there is NO general jus soli — being born on Swiss territory confers no citizenship by itself. Acquisition is automatic and operative by law: no application, no administrative grant, and no cantonal or communal decision is required; the civil-registry and passport steps are merely declaratory. The constitutional anchor is BV Art 38(1), under which the Confederation regulates acquisition of citizenship by descent, and BV Art 37(1), which defines a Swiss citizen as a person holding the citizenship of a commune AND of a canton (/071). By operation of Art 2 BueG the child simultaneously acquires the cantonal (Kantonsbuergerrecht) and communal (Gemeindebuergerrecht / Heimatort) citizenship of the transmitting Swiss parent, so the single birth event produces citizenship at all three levels at once. This is a signature route in the CH knowledge base.

A child is a Swiss citizen from birth in the following cases (BueG Art 1, /002): (1) Art 1(1)(a) — the child of married parents where the father OR the mother is a Swiss citizen at the child's birth; gender-neutral, so a Swiss mother transmits on equal footing with a Swiss father. (2) Art 1(1)(b) — the child of a Swiss-citizen mother who is not married to the father; acquisition is automatic regardless of the father's nationality. (3) Art 1(2) — the minor foreign child of an unmarried Swiss FATHER acquires Swiss citizenship through the later establishment of the parent-child relationship (Kindesverhaeltnis) to the father, treated as if acquisition had occurred at birth; the ONLY condition is that the child is MINDERJAEHRIG (a minor, under 18) when filiation is established — there is NO age-22 limit (age 22 is the separate Art 24 child-of-naturalised cap; this Art 1(2) filiation acquisition is carried as a related route, see cross-references). (4) Art 1(3) — where such a minor child has its own children, they too acquire Swiss citizenship. There is NO residence requirement and NO place-of-birth requirement: birth may occur inside or outside Switzerland. The only standing automatic-loss mechanism for a birth-acquired Swiss who is born abroad and holds another nationality is the BueG Art 7 forfeiture at completed age 25 if retention is not reported/declared (age 25, NOT 22 — C6); that mechanism is carried at CH-DSC-03 / CH-OPSC-03 and cross-referenced here.

Because acquisition is automatic, there are no eligibility 'requirements' in the naturalisation sense — only proof-of-status conditions used to register the child and obtain documents (BueG Art 1). The substantive conditions are: (a) a qualifying parent-child link to a Swiss citizen at the determining moment — married-parent transmission by either parent (Art 1(1)(a)), unmarried Swiss mother (Art 1(1)(b)), or established filiation to an unmarried Swiss father while the child is a minor (Art 1(2)); (b) the transmitting parent must actually have held Swiss citizenship at the child's birth (a parent who had earlier lost Swiss citizenship — e.g. through the pre-1992 single-nationality regime or an Art 7 born-abroad forfeiture — cannot transmit, /035); and (c) for the Art 1(2) case, minority of the child at filiation. There is NO residence, language, financial, integration or security requirement — those belong to naturalisation routes (CH-NAT-01), not to birth acquisition. The cantonal/communal citizenship cascades automatically (Art 2); no cantonal 2-5y residence applies (the 2-5y BueG Art 18 cap is an ordinary-naturalisation rule, C3).

Documents typically used to evidence and register Art 1 acquisition (declaratory): the child's birth certificate; the Swiss-citizen parent's valid Swiss passport or identity card (proof the parent held Swiss citizenship at the child's birth); the parents' marriage certificate where transmission is via Art 1(1)(a) (married parents); for the Art 1(1)(b) and Art 1(2) unmarried-parent cases, the document establishing maternity/paternity — for the Art 1(2) unmarried-Swiss-father route, the Kindesanerkennung (acknowledgment of paternity) or judicial paternity judgment establishing the Kindesverhaeltnis while the child is a minor. For births abroad these are submitted to the Swiss representation, which forwards them for entry in Infostar; the transmitting parent's Heimatort (cantonal+communal citizenship) is recorded per Art 2. Where citizenship status is doubtful in a multi-generational abroad-born line, the declaratory Feststellungsverfahren under BueG Art 43 can be used to clarify status (canton of the doubtful citizenship decides; SEM may also apply) — carried at CH-CBN-04. No federal naturalisation fee arises (the federal fees in BueV Art 25 apply to naturalisation, not to ex-lege birth acquisition); only passport/identity-document and consular-service fees apply.

Acquisition under Art 1 BueG is ex lege (by operation of law): the citizenship exists from the moment of birth and the administrative acts are declaratory, not constitutive. The practical steps are: (1) Birth registration in the Swiss civil register (Zivilstandsregister / Infostar) — for a birth in Switzerland via the cantonal civil-registry office; for a birth abroad via the competent Swiss representation (embassy/consulate), which transmits the birth notification to the home civil-registry office. (2) Heimatort entry — the transmitting Swiss parent's cantonal and communal citizenship is co-recorded by operation of Art 2 BueG. (3) Establishment of filiation where required — for the Art 1(2) unmarried-Swiss-father case, the Kindesverhaeltnis (recognition/Anerkennung or judicial paternity) must be established while the child is a minor; on establishment, Swiss citizenship is treated as having existed from birth. (4) Swiss identity documents — the guardian/parent applies for a Swiss passport and/or identity card at the Swiss representation (abroad) or the cantonal passport authority (in Switzerland). (5) For a child born abroad who is a dual national: note the future BueG Art 7 retention duty — the person must report/declare retention to a Swiss authority before completing age 25 or forfeit Swiss citizenship (age 25 per C6, /037); this is administered through the Auslandschweizerregister (ASG Art 11) and is cross-referenced to CH-OPSC-03.

The operative statute is BueG Art 1 (Erwerb durch Abstammung), decoded verbatim: 'Schweizer Buergerin oder Buerger ist von Geburt an: a. das Kind, dessen Eltern miteinander verheiratet sind und dessen Vater oder Mutter Schweizer Buergerin oder Buerger ist; b. das Kind einer Schweizer Buergerin, die mit dem Vater nicht verheiratet ist'. Art 1(2): the minor foreign child of an unmarried Swiss father acquires citizenship 'durch die Begruendung des Kindesverhaeltnisses zum Vater.. wie wenn der Erwerb mit der Geburt erfolgt waere'. Art 2 (Kantons- und Gemeindebuergerrecht) provides that with Swiss citizenship the child acquires the cantonal and communal citizenship of the Swiss parent; where both parents are Swiss, the child takes the cantonal/communal citizenship of the parent whose surname it bears. The constitutional foundation is BV Art 38(1) — 'Der Bund regelt Erwerb und Verlust der Buergerrechte durch Abstammung, Heirat und Adoption' (/072) — and BV Art 37(1), which makes federal Swiss citizenship derivative of a communal AND cantonal citizenship (/071). The temporal anchor is BueG Art 50 (Nichtrueckwirkung / non-retroactivity): acquisition is governed by the law in force at the determining event (the birth), so pre-2018 births are governed by the then-applicable BueG 1952 text. Dual citizenship has been freely permitted since 1992-01-01, so a child may hold Swiss plus another nationality without restriction (domestic reform BG 1990-03-23).

Several adjacent matters bear on a birth-acquisition claim. (1) Non-retroactivity: a claim is governed by the law in force at the birth (BueG Art 50). Pre-2018 births fall under the BueG 1952 text; pre-equality cohorts (foreign children of Swiss mothers born pre-1992; foreign children of unmarried Swiss fathers born before 2006-01-01) did not always acquire automatically under the then-gendered descent rules and are remedied through the Art 51 transitional facilitation — carried at CH-DSC-02 / CH-HIS-01, not under Art 1 itself. (2) Loss by annulment of filiation: if the Kindesverhaeltnis to the transmitting parent is later set aside, Swiss citizenship is lost by law UNLESS the child would thereby become stateless (BueG Art 5). (3) Born-abroad dual-national forfeiture: a birth-acquired Swiss born abroad who also holds another nationality must report/declare retention before completed age 25 or forfeit (BueG Art 7, age 25 per C6 — NOT 22; the 22 figure belongs to the repealed 1952 Art 10, /058); forfeiture cascades to that person's own children (Art 7(2)) and to the cantonal/communal layer (Art 8). (4) Dual citizenship is freely permitted since 1992-01-01, so a child can hold Swiss plus a foreign nationality from birth with no obligation to choose. (5) Adopted minors acquire by the distinct Art 4 route (CH-ADP-01), not Art 1.