This is really tough, and the question relies on the nature of your organization. If your organization is well-run and has clear escalation paths, then you fol

This is really tough, and the question relies on the nature of your organization. If your organization is well-run and has clear escalation paths, then you follow the process, and the process will sort out the situation out for you. If there are no such processes in place in your organization, then you either rely on your direct relationship with that guy's boss (if you have one), or more commonly, escalate to your own manager, and your own manager dialogues with that guy's manager.