This article uses the introduction of biometric passports in the European Union (EU) as a case study in order to illustrate how the Swiss democratic system and the updating of the Schengen Agreement work together in practice.
If the contents of such an act or measure can become binding on Switzerland only after the fulfilment of constitutional requirements, Switzerland shall inform the Council and the Commission of this at the time of its notification. Switzerland shall promptly inform the Council and the Commission in writing upon fulfilment of all constitutional requirements. Where a referendum is not required, notification shall take place as soon as the referendum deadline expires. If a referendum is required, Switzerland shall have a maximum of two years from the date of the Council's notification within which to make its notification. From the date laid down for the entry into force of the act or measure for Switzerland and until it has given notification that the constitutional requirements have been met, Switzerland shall, where possible, implement the act or measure in question on a provisional basis.
And now to the introduction of the biometric passport in the EU and in Switzerland: in order to improve document security and to prevent falsification of documents, the EU on 13 December 2004 adopted Regulation 2252/2004 concerning security features and biometrics in passports and travel documents.  The EU's biometric passport includes information about the bearer's face and the fingerprints.
As regards Switzerland, this Regulation constitutes a development of the provisions of the Schengen acquis within the meaning of the Agreement signed between the European Union […] and the Swiss Confederation concerning the association of the Swiss Confederation with the implementation, application and development of the Schengen acquis […].
The adoption of the Regulation was duly notified to Switzerland. There, the Federal Government proposed the acceptance of the update and presented draft legislation to that effect. In 2008, the Swiss Federal Parliament adopted the legislation (actually, not only because of the Schengen context but also because the United States of America demanded the use of biometric passports).
However, in the same year, a popular referendum was launched against the new rules. Behind the referendum was an interesting coalition of right, left and green parties. They shared a fear of security risks arising from the central storage of data, for which the Swiss legislation provided far-reaching rules that were not prescribed by EU law. According to the referendum committee, the Swiss people should be able to choose between a traditional and a biometric passport. The committee succeeded in collecting the necessary 50'000 signatures, which meant that a popular vote had to be held.
The vote was preceded by a lively campaign. Voting took place on 17 May 2009. The people were asked whether or not they agreed to the introduction of the biometric passport. 50,1 % of the votes cast were in favour and 49,9 % against. The difference between yes and no was a mere about 5'000 votes, the closest result at that time since the establishment of the modern Swiss state in 1848.
As a result of the vote, the new rules entered into force on 1 March 2010 and the new type of passport was introduced in Switzerland.
Note that otherwise the Swiss passports do not follow the EU model. The EU Member States have decided in favour of a common model also in other respects, including the outward appearance of the passports (colour etc.).
 Regulation 2252/2004/EC on standards for security features and biometrics in passports and travel documents issued by Member States, OJ 2004 L 385/1.