This policy restricts users on a machine to the specified list of user locales. If the list is empty, it locks all user locales ...

This policy restricts users on a machine to the specified list of user locales. If the list is empty, it locks all user locales to their current values. This policy does not change existing user locale settings; however, the next time a user attempts to change their user locale, their choices will be restricted to locales in this list.

To set this policy on a per-user basis, make sure that the per-machine policy is set to not configured.

The locale list is specified using language tags, separated by a semicolon (;). For example, en-US is English (United States).  Specifying "en-CA;fr-CA" would restrict the user locale to English (Canada) and French (Canada).

If this policy is Enabled, then only locales in the specified locale list may be selected by users.

If this policy is Disabled or Not Configured, then users may select any locale installed on the machine, unless restricted by the "Disallow selection of Custom Locales" policy.

If this policy is Enabled at the machine level, it cannot be disabled by a per-user policy. If this policy is disabled at the machine level, then the per-user policy will be ignored. If this policy is not configured at the machine level, then restrictions will be based on per-user policies.

Note that if an administrator has enabled the "Disallow selection of Custom Locales" policy, then users will be prevented from selecting supplemental custom locales, even if they are in the specified locale list for this policy.