This is mandated in Article 8 of this ILO convention: http://www.ilo.org/dyn/normlex/en/f?p=NORMLEXPUB:12100:0::NO... http://www.ilo.org/dyn/normlex/en/f?p=1000:11300:0::NO:11300...

This is Switzerland and part of the OR ("Obligationenrecht"), §329c, paragraph 1 [0]

[0] https://www.admin.ch/opc/en/classified-compilation/19110009/...

The law in Germany pretty much states the same.