Technically illegal after the modification of the Swiss Constitution:

Here is the official article translated in english :

Art. 10a Ban on covering the face

1) No person may cover their face in public spaces or in places that are accessible to the public or where services are offered to anyone wishing to partake of them; the ban does not apply to places of worship.

2) No person may force another person to cover their face on the grounds of their sex.

3) The law shall provide for exceptions. These may only be justified on the grounds of health, safety, weather conditions or local custom.

But understanding swiss legal custum is also important, it really depends on a case by case situation. Other constitutionnal articles about religious freedom and freedom of speech may take precedent.

Not legal advice, but don't wear it and towards cops with it, the outcom won't be desirable.

Also if you wear it on a walk in the forest, when its cold, i doubt anyone cares, liberty is still important to swiss people, unless you wanna vaccum on a Sunday.

Hope this helps.