Control who can delete Media Library files on a WordPress site on the basis of a capability

restrict_media_permissions.php

</php
// In this example, only logged-in users with the 'activate_plugins' capability will be able to delete files shown in the Media Library.
// (By default, only administrators have this capability.)
// This code should be put in functions.php or in a plugin.
add_action('delete_attachment', array($this, 'restrict_media_deletion_permissions'), 1);
public function restrict_media_deletion_permissions($post_id) {
	if (! current_user_can('activate_plugins')) {
		?>
		<script type="text/javascript">alert("You do not have permission to delete media files.");</script>
		<?php
		die();
	}
}
?>