fancontrol-gui/helper/fancontrol.gui.helper.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 user root can own the foo helper -->
  <policy user="root">
    <allow own="fancontrol.gui.helper"/>
  </policy>

</busconfig>