Manual:$wgAllowCopyUploads

Details
Users also need to have the associated [[Special:MyLanguage/Manual:$wgGroupPermissions|user right] before this option is available. the permission needs to be granted explicitly.

By default, upload by URL are only possible using the upload>Special:MyLanguage/API:Upload|API (or extensions such as ).

To make the option usable from Special:Upload, you need to set  to true as well.

Example usage
This example setup will allow all autoconfirmed users to upload by URL, via Special:Upload or the API.

Add to the bottom of your :