If the application choses to do so. Installation used to require root and I don't see a way who root could prevented from be enabling a systemd service. Short o

If the application choses to do so. Installation used to require root and I don't see a way who root could prevented from be enabling a systemd service. Short of having a signed read-only rootfs which no common distro has. Nowadays you don't even need root to install something that runs a every login: There is the user instance of systemd. Of course without root those services are limited in what they can do.