MediaWiki extension to allow restricting page creation per namespace.
Set minimum permissions required for creating pages in each namespace. If multiple permisison are listed, a user needs to have all of them to create pages in that namespace, along with 'createpage' and (if a talk page) 'createtalk'.
Default is no per-namespace create restrictions, although NS_MEDIAWIKI is restricted via the 'editinterface' permission.
Restrict creating pages in the main namespace to registered users
$wgNamespaceCreateProtection = array( NS_MAIN => 'createmain' );
$wgGroupPermissions['*']['createmain'] = false;
$wgGroupPermissions['user']['createmain'] = true;
Alternatively, per namespace protection can be an array of permissions
$wgNamespaceCreateProtection = array( NS_MAIN => array( 'createmain', 'human' ) );