The VisualEditor interface does not currently recognize page protection. If a user visits a protected page (a page to which he or she does not have access to edit), VisualEditor will still display a working edit form and the first click of the "Save page" button will work. It will produce a dialog box that will present a second "Save page" button that does not work. Ideally, VisualEditor would not let a user get this far without indicating that the page is uneditable.
Related to this, there's no warning for administrators that a page is protected when they're editing the page. This may be a separate bug, however.