Suicidal code

Have you seen code that's so bad if it had any feeling it would trigger an EMP next to the source control server to commit suicide? Well, I have. And here is an example:

 public synchronized void invoke(AbstractCommand command)
 {
    if (command == null) return;
    remoteDoIt(command);
    if (command instanceof Undo)
    {
       undo();
       return;
    }
    if (command instanceof Redo)
    {
       redo();
       return;
    }
    if (command instanceof Update)
    {
       command.doIt();
       return;
    }
    if (command.doIt())
    {
       history.addLast(command);

       if (redo.size() > 0)
       {
          redo.clear();
       }
    }
    else
    {
       history.clear();
       updates.clear();
    }
 }

To make matters worse, Undo, Redo and Update are all empty "marker" interfaces. Refactor this!