You are not forbidden at the Federal level to have fixed units. But many states do indeed requires a permit to install fixed units. And have strict regulations

You are not forbidden at the Federal level to have fixed units. But many states do indeed requires a permit to install fixed units. And have strict regulations such as self producing half of the electricity required by the installation. Here are a few examples of such regulations: - Geneva (the most strict state): https://www.ge.ch/installations-techniques-rafraichissement/climatisation-confort https://www.ge.ch/installations-techniques-rafraichissement/... - Fribourg: https://bdlf.fr.ch/app/fr/texts_of_law/770.1/art/16 https://bdlf.fr.ch/app/fr/texts_of_law/770.1/art/16 - Vaud: https://www.vd.ch/fileadmin/user_upload/themes/environnement/energie/fichiers_pdf/FAQ-batiment-energie-nov19.pdf https://www.vd.ch/fileadmin/user_upload/themes/environnement... One of the side effect of such regulation is that many business and houses will use cheap non-fixed units with open door and windows instead of installing proper reversible heat pumps.