When Emacs is run from the OS X GUI (the dock, spotlight, finder, etc.)
in OS X it doesn't set the locale correctly.

Here's the output of C-h C RET on my machine with no user configuration:

Coding system for saving this buffer:
  Not set locally, use the default.
Default coding system (for new files):
  nil
Coding system for keyboard input:
  = -- no-conversion (alias: binary)

Coding system for terminal output:
  nil
Coding system for inter-client cut and paste:
  nil
Defaults for subprocess I/O:
  decoding: U -- utf-8-unix (alias: mule-utf-8-unix)

  encoding: U -- utf-8-unix (alias: mule-utf-8-unix)


Priority order for recognizing coding systems when reading files:
  1. utf-8 (alias: mule-utf-8)
  2. iso-2022-7bit 
  3. iso-latin-1 (alias: iso-8859-1 latin-1)
  4. iso-2022-7bit-lock (alias: iso-2022-int-1)
  5. iso-2022-8bit-ss2 

I've snipped off the rest, if you want it I can provide it.

Emacs relies on LC_ALL, LC_CTYPE or LANG being set, and OS X's terminal
application sets the LANG environment variable. OS X doesn't set any of
these variables when the application is run from the GUI.

Additionally, Emacs detects when it's being run from the OS X terminal
(mule-cmds.el line 2722) and hard-codes some settings.

The Windows version of Emacs has a similar problem and solves this by
running an "init_environment" function from main in emacs.c that uses
the Windows APIs to set the LANG variable. (as described at
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=3221#32)

I've written a patch that copies this functionality but for NextStep.
c-h C RET gives:

Coding system for saving this buffer:
  Not set locally, use the default.
Default coding system (for new files):
  1 -- iso-latin-1-unix (alias: iso-8859-1-unix latin-1-unix)

Coding system for keyboard input:
  1 -- iso-latin-1-unix (alias: iso-8859-1-unix latin-1-unix)

Coding system for terminal output:
  1 -- iso-latin-1-unix (alias: iso-8859-1-unix latin-1-unix)

Coding system for inter-client cut and paste:
  nil
Defaults for subprocess I/O:
  decoding: U -- utf-8-unix (alias: mule-utf-8-unix)

  encoding: U -- utf-8-unix (alias: mule-utf-8-unix)


Priority order for recognizing coding systems when reading files:
  1. iso-latin-1 (alias: iso-8859-1 latin-1)
  2. utf-8 (alias: mule-utf-8)
  3. iso-2022-7bit 
  4. iso-2022-7bit-lock (alias: iso-2022-int-1)
  5. iso-2022-8bit-ss2 

Which looks better to me. It also gives me A4 paper instead of legal and
ispell/hunspell is better behaved.