Limiting different users on a single machine to different connectivity
Well, I cracked it, it wasn't loginHooks I needed, but launchctl.

Basically, create two scripts (executable of course, you can make em root only too):

User1.sh 


  !/bin/bash   ifconfig en0 up; ifconfig en1
  down;


User2.sh  


  !/bin/bash   ifconfig en1 up; ifconfig en0
  down;


These of course make the assumption you're using an imac, en0 is the enthernet, en1 is the WiFi.

Then create a plist file (with root ownership, 644), mine was this:

User1's went in /Users/user1/Library/LaunchAgents/org.user1.plist

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
    &lt;key&gt;Label&lt;/key&gt;
    &lt;string&gt;org.user1.plist&lt;/string&gt;
    &lt;key&gt;ProgramArguments&lt;/key&gt;
    &lt;array&gt;
        &lt;string&gt;/Users/user1/bin/User1.sh&lt;/string&gt;
    &lt;/array&gt;
    &lt;key&gt;RunAtLoad&lt;/key&gt;
    &lt;true/&gt;
&lt;/dict&gt;
&lt;/plist&gt;


User2's in /Users/user2/Library/LaunchAgents/org.user2.plist

 &lt;?xml version="1.0" encoding="UTF-8"?&gt;
    &lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
    &lt;plist version="1.0"&gt;
    &lt;dict&gt;
        &lt;key&gt;Label&lt;/key&gt;
        &lt;string&gt;org.user2.plist&lt;/string&gt;
        &lt;key&gt;ProgramArguments&lt;/key&gt;
        &lt;array&gt;
            &lt;string&gt;/Users/user2/bin/User2.sh&lt;/string&gt;
        &lt;/array&gt;
        &lt;key&gt;RunAtLoad&lt;/key&gt;
        &lt;true/&gt;
    &lt;/dict&gt;
    &lt;/plist&gt;


After that run


  sudo launchctl load -w
  /Users/user1/Library/LaunchAgents/org.user1.plist


and 


  sudo launchctl load -w
  /Users/user2/Library/LaunchAgents/org.user2.plist


as each user.

That's it, it's quick, simple, and if you set the owner of the scripts as someone else (and on another path), it's fairly secure (not bulletproof, but that's not in my scope at the moment).