You already answered yourself; via Group Policy.
See http://www.howto-outlook.com/howto/policies.htm

Signature
Robert Sparnaaij [MVP-Outlook]
Coauthor, Configuring Microsoft Outlook 2003
http://www.howto-outlook.com/
Outlook FAQ, HowTo, Downloads, Add-Ins and more
http://www.msoutlook.info/
Real World Questions, Real World Answers
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> How does one prevent a users from using the archive function within
> Outlook 2007?
[quoted text clipped - 3 lines]
> Thanks in Advance,
> Eric Sabo