Description of problem:
It appears that doing localectl set-locale as root works globally. Doing as user changes locale settings but the locale after login is still what root has initially set.

I would expect that changes by root would affect whole system and changes by user would affect only the particular user. That means after user sets locale, new shells will use that locale for the particular user. See current behavior:

# localectl set-locale LANG=C.utf8
// now system locale changed to C.utf8
// lets do as a user
$ localectl set-locale LANG=bg_BG.utf8
// then in a new shell
$ locale
LANG=C.utf8
LC_CTYPE="C.utf8"
LC_NUMERIC="C.utf8"
LC_TIME="C.utf8"
LC_COLLATE="C.utf8"
LC_MONETARY="C.utf8"
LC_MESSAGES="C.utf8"
LC_PAPER="C.utf8"
LC_NAME="C.utf8"
LC_ADDRESS="C.utf8"
LC_TELEPHONE="C.utf8"
LC_MEASUREMENT="C.utf8"
LC_IDENTIFICATION="C.utf8"
LC_ALL=
$ localectl
   System Locale: LANG=bg_BG.utf8
       VC Keymap: us
      X11 Layout: us,bg
     X11 Variant: ,phonetic
     X11 Options: grp:alt_shift_toggle

Even worse as root:
# localectl status
   System Locale: LANG=bg_BG.utf8
       VC Keymap: us
      X11 Layout: us,bg
     X11 Variant: ,phonetic
     X11 Options: grp:alt_shift_toggle


Version-Release number of selected component (if applicable):
systemd-229-8.fc24.x86_64

I'm not even sure if there's any security implication here.