Switzerland has enacted the "Federal Law on the Use of Electronic Means for the Fulfilment of Governmental Tasks" (EMBAG), establishing a mandatory requirement for open source software within public sector bodies.
Soweit möglich und sinnvoll sind international etablierte Lizenztexte zu verwenden. Haftungsansprüche von Lizenznehmern sind auszuschliessen, soweit dies rechtlich möglich ist.
As far as possible and expedient, internationally established licenses are to be used.
That sounds like they're not mandating specific licenses, but the GPL is a reasonable choice
The only problem is that there are a number of licenses that purport to be open source, but which don't meet established definitions of the term. The license for Grayjay comes to mind. I'd hope that they blacklist certain licenses like that, rather than enforcing a specific one.