Gnome15/data/dbus/g15-system-service.conf

<!DOCTYPE busconfig PUBLIC
 "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
 "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>

  <!-- Only root can own the service -->
  <policy user="root">
    <allow own="org.gnome15.SystemService"/>
    <allow send_destination="org.gnome15.SystemService" send_interface="org.gnome15.SystemService"/>
    <allow send_destination="org.gnome15.SystemService" send_interface="org.freedesktop.DBus.Introspectable"/>
  </policy>

  <policy at_console="true">
    <allow send_destination="org.gnome15.SystemService" send_interface="org.gnome15.SystemService"/>
    <allow send_destination="org.gnome15.SystemService" send_interface="org.freedesktop.DBus.Introspectable"/>
  </policy>

  <policy context="default">
    <allow send_destination="org.gnome15.SystemService" send_interface="org.gnome15.SystemService"/>
    <allow send_destination="org.gnome15.SystemService" send_interface="org.freedesktop.DBus.Introspectable"/>
  </policy>

</busconfig>