config.keystrokes = [
     [ 9, 'disableTab' ] // disable TAB key to avoid nesting!
];

config.blockedKeystrokes = [ 9 ];

for (instance in CKEDITOR.instances) {
    var editor = CKEDITOR.instances[instance];
    editor.setKeystroke(9, false);
}

editor.on('key', function(e) { alert ("hi"); return false; });

requires: 'indentlist',

indentlist: 1,
indentblock: 1,

editor = CKEDITOR.replace( 'element_name' );

editor.on('key', function(e) {
var key = e.data.keyCode;
if(key==9) {
return false;
}

editor.on('key', function (evt) {
    if (editor.mode != 'wysiwyg') {
        return false;
    }

    if (evt.data.keyCode == this.indentKey || evt.data.keyCode == 9) {
        evt.cancel();
        return false;
    }
}, null, null, 1);

editor.on('key', function (evt) {
    var path = editor.elementPath();

    if (editor.mode != 'wysiwyg') {
        return false;
    }

    if (evt.data.keyCode == this.indentKey || evt.data.keyCode == 9 && path.contains('ol')) {
        evt.cancel();
        return false;
    }
}, null, null, 1);