This allows admins to restrict weapons. It does not repay the player if it removes a weapon.
The other issue, is if players have a weapon out when it's restricted, it just stops working. It loses it's ammo display, and will not fire.
Usage:
Add "admin_restrict weapon_knife" or whatever to your server.cfg. You can have up to 32 restrictions at a time. Use "admin_unrestrict weaponname" to unrestrict a weapon.
http://devicenull.org/sm_plugins/restriction.sp