The mentioned legal basis is [1].
Note that this applies strictly to downloading though. Participating in a torrent swarm (where uploading is also happening) is not permitted. That's where the technicality you mention comes in: until recently, it was illegal to monitor internet users for copyright enforcement purposes, which meant it was illegal to monitor a torrent swarm, which meant you could somewhat safely seed torrents, despite it being illegal.
That loophole was recently removed however.
[0]: https://www.ige.ch/en/intellectual-property/counterfeiting-a...
[1]: https://www.fedlex.admin.ch/eli/cc/1993/1798_1798_1798/en#ar...
De jure it's not really legal anymore since they updated the law... De facto nobody cares as long as you're not making a business out of it.
Same goes for the place I live since 2016: Thailand.
Though: Not pirating for professional stuff, only for private stuff. I still support software/media by buying the things I want to support.
My claim was founded on authoritative sources, including the law itself. If you want to contradict that claim, you'll need to back it up.
Please note too, piracy is not legal in Switzerland. What is illegal is the spying and tracking which would be necessary to build a case and prosecute pirates. Technically you could still self-incriminate if you documented all of your piracy, with proof, and published it online.