Good timing! I was actually trying to do this on an FxTextArea control in Flex Gumbo the other day and it looks like it may not be possible. I was also able to reproduce the issue with a standard Flash Player TextField instance, so filed a bug report in the public Flash Player bug base:
http://bugs.adobe.com/jira/browse/FP-1094

Peter

I have a weird problem with the context menu. I`m trying to hide the clipboardItems (cut, copy…) from a textArea`s context menu. And it still appears. I`d appreciate any answers that might help. My code is below:

private function init():void
{
    var cm:ContextMenu = new ContextMenu();
    cm.hideBuiltInItems();
    cm.clipboardMenu = false;
    cm.clipboardItems.copy = true;
    cm.clipboardItems.cut = true;
    cm.clipboardItems.paste = true;
    cm.clipboardItems.selectAll = false;

    var m1:ContextMenuItem = new ContextMenuItem("Mark as Company Name" );
    var m2:ContextMenuItem = new ContextMenuItem("Mark as Industry" );
    var m3:ContextMenuItem = new ContextMenuItem("Mark as Location" );
    var m4:ContextMenuItem = new ContextMenuItem("Mark as Cost" );
    var m5:ContextMenuItem = new ContextMenuItem("Mark as Market Value" );

    m1.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, mark);
    m2.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, mark);
    m3.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, mark);
    m4.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, mark);
    m5.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, mark);
    cm.customItems.push(m1, m2, m3, m4, m5);

    panelParsedText.contextMenu = cm;
}