Generally, that's a bad practice, because it can potentially bypass system security.
Be that as it may...
I tripped over this entry in SunBlogs, from 19-OCT-05
<a href="http://blogs.sun.com/roller/page/bnitz/20051019" target="_blank">http://blogs.sun.com/roller/page/bnitz/20051019</a>
It describes one approach to this topic.
It is for OpenSolaris but may be applicable to the non-open-source variety.
Give it a try.
To do this with Solaris 9 and RBAC using one of the default profiles:
usermod -P "Maintenance and Repair" <username>
Then when the user <username> wants to shutdown the system they type:
pfexec /usr/sbin/halt
There's a few other things they can execute with this profile such as "eeprom" "vmstat" "crash" so you may want to look at making your own profile.
have a look here for more info http://docs.sun.com/app/docs/doc/817-0365/6mg5vpmbd#hic