I would say that in Switzerland the right to breastfeed is guaranteed indirectly through article 11 of the Constitution, which states that 'children and adolescents have the right to special protection of the personal integrity and to promotion of their development', because this article reaffirms the relevant provisions in the international law on the right to nutrition, notably the Convention on the Rights of the Child (which came into force in 1990), in which two articles address this issue.
Article 24 of the Convention says that "States Parties recognize the right of the child to the enjoyment of the highest attainable standard of health . . .(paragraph 1)" and shall take appropriate measures "to combat disease and malnutrition . . . . through the provision of adequate nutritious foods, clean drinking water, and health care (paragraph 2c).” Article 24 also says that States Parties shall take appropriate measures . . . “to ensure that all segments of society, in particular parents and children, are informed, have access to education and are supported in the use of basic knowledge of child health and nutrition [and] the advantages of breastfeeding . . . .“ Article 27 says that States Parties "shall in case of need provide material assistance and support programmes, particularly with regard to nutrition, clothing, and housing (paragraph e)."
Breastfeeding would fall under the provisions of the articles above becuase it is a form of nutrition, but it can also be regarded as a kind of health service because of the fact that it reduces the risk of a broad variety of diseases.
In relation to breastfeeding, the state of course cannot fulfill the right directly, but it can respect, protect, and facilitate. This means that Switzerland, as a Party to the Convention, has taken the obligation to protect both the right of the child to be breastfed and the right of the mother to breastfeed.
Of course, each country decides how this right is guaranteed by adopting appropriate legislative and policy measures and I would guess that in countries where there are practical obstacles to the fuilfilment of this right and where voluntary codes do not work, legislatures are sometimes compelled to act to reaffirm it (this is what happened in Scotland, for example, through the Breastfeeding Bill of 2004).
I do not think that Switzerland has reaffirmed the right to breastfeed in public explicitly in any of its laws. Possibly it is because it is not really a contested issue in the same way it is in Anglo-Saxon countries, so there was no practical need for this particular right to be codified. With respect to jurisprudence, as far as I could see no cases of discrimination regarding breastfeeding mothers have been brought to courts (while I could not possibly check all lower-instance court decisions, I checked both the Federal Tribunal and the European Court of Human Rights database).