Quoting Adam Borowski (kilobyte@???):

> An orderly shutdown is better than an unclean one, thus any display
> manager that forbids local users to shutdown is buggy.

Let me tell you a metaphor, to sneak up on why it's not that simple.

I have a sign at the entrance to my garden. For context, for forty
years from 1966 to 2006, my family home was a rental property, after my
father's employer, Pan American World Airways, moved us to Hong Kong.
Finally, I got back, and moved back in. During those forty years of
renter neglect, numerous people had gotten used to walking, or even
walking with their dogs, from the street through the wilder part of my
large front yard.

Most of the sidewalk border is blocked by 20 year old oleander bushes,
about three meters tall. There was one gap in the oleanders about a
meter wide at one end, another about 30cm wide at the other. Even after
I reclaimed the area behind the oleanders from wildness and planted a
vegetable garden in raised beds, people kept barging through, often with
their dogs. If I engaged their attention and politely asked them to
leave, they'd almost always say the same thing: 'I thought this was a
park.'

They didn't really think it was a park. For 40 years, they assumed it
was a partially derelict property that they could trespass on without
objection -- but when you corner people and they're totally in the
wrong, they blurt out the first justification that comes to mind.

I said, this is a social problem: Time for a technical solution
(ref: http://linuxmafia.com/~rick/lexicon.html#edwards).

I put a two-meter-tall steel-wire-frame arch in the large gap, like an
upside-down U, turning it into a formal entrance, and planted climbing
roses to ascend up each side. And just above eye-level in the arch,
facing the street, a sign:

         INVITED GUESTS WELCOME.
  1105 Altschul Gardens is private prperty.

It was cordial, and it was clear. Suddenly the gap wasn't just a gap,
but an entrance, ostentatiously looked after, curated. The arch and
sign jointly conveyed: No more 'oh, sorry' excuses. You assume this
is derelict at your peril.

We had no more problems except one teenager who said 'Oh, I'm not
invited?' with a stupid smirk. I just looked bored and escorted him
off.

The linneus bottomus: The purpose of the sign wasn't to prevent
trespassing. It was to create undeniable awareness. Mindfulness.

The purpose of a display manager not making it a trivially easy
operation for any local user to initiate software shutdown isn't to
prevent shutdown. It's to discourage _mindless_ shutdown, by console
users perhaps unaccustomed to Unix and oblivious to the cron task or
long-running program they're going to kill by thinking like a pee-cee
weenie who assumes he/she is the centre of the friggin' world and nobody
else matters.

It means no more 'oh, sorry' excuses. You assume this system's run
state is unimportant at your peril. The linneus bottomus: The purpose
of making such software shutdown not trivially easy wasn't to prevent
shutdown. It is to create undeniable awareness. Mindfulness.

The standard solution to give users _deliberately_ that software access
is to add them to a group with that right.

If the user wants to ignore social cuing and shutdown the machine anyway
by hardware measures, that's indeed always possible at the local
machine and social cuing won't stop it. If neighbours want to ignore
social cuing and stomp through my vegetable garden, that's indeed always
possible from the sidewalk and social cuing won't stop it.