Permit use of Environment preference extension This policy setting allows you to permit or prohibit use of the Environment preference extension. When a preference extension is prohibited, it does not appear in the Group Policy Management Editor window of the GPMC. If you enable this policy setting, you permit use of the preference extension. Enabling this policy setting overrides the 'Restrict users to the explicitly permitted list of snap-ins' policy setting. If you disable this policy setting, you prohibit use of the preference extension. If you do not configure this policy setting, you permit use of the preference extension unless restricted by the 'Restrict users to the explicitly permitted list of snap-ins' policy setting.

(1) GPO: User Configuration\Administrative Templates\Windows Components\Microsoft Management Console\Restricted/Permitted snap-ins\Group Policy\Preference snap-in extensions!Permit use of Environment preference extension (2) REG: HKEY_CURRENT_USER\Software\Policies\Microsoft\MMC\{35141B6B-498A-4cc7-AD59-CEF93D89B2CE}!Restrict_Run