From: Ethan Benson <erbenson@alaska.net>

Currently Linux allows the use of the utime() and utimes() syscalls on
immutable or append-only files, this is incorrect.

utime{s}() is not supposed to work if you lack write access to a file,
in the case of an immutable file NOBODY has write access.

for an append-only file it only makes sense to be able to update its
time to present, not the past.

I have checked BSD, and they implement the behavior I propose, for
immutable files utime() and utimes() fail.  for append-only files they
fail if the time argument is not NULL.