Thread:Project:Current issues/lock special sites/reply

That's not possible so easy (there is no built in function to this as a user/admin) :)

You can use this example as a basis and check in this function for the actual user rights. But note, that this will only prevent the page being listed on Special:SpecialPages. If someone knows the URL, he can still access this special page directly. To prevent the access, you need to edit the special page's source code, but before you do this, read Do not hack MediaWiki core.