If you have administrators-in-training, you can prevent them from using the registry tools. Using Regedt32:

Highlight HKEY_USERS and Load Hive from the Registry menu. Browse to their profile directory and select NTUser.dat. When prompted for Key Name, input their UserID. Navigate to \Software\Microsoft\Windows\CurrentVersion\Policies. If no System sub-key exists, Add Key. Then Add Value of DisableRegistryTools (under the System key) using type REG_DWORD and set it to 1. Unload Hive from the Registry menu.

Your junior administrator will not be able to run Regedt32 or Regedit.