The evidential weight of testimonial evidence varies with the epistemic status of testifiers. The words of more competent testifiers have more weight than those of less competent ones. This much is uncontroversial. Recently, it has been argued that testimonial evidence may even have preemptive force, i.e. it provides the recipient with evidence that makes her further evidence rationally unusable. In such a case, the testifier will be an epistemic authority for the recipient. In my talk, I will consider two old and one new argument in favor of epistemic authority. I will argue that whereas arguments from trust (Keren) and track record (Raz, Zagzebski) fail to establish epistemic authority, the argument from higher-order defeat will fare better. I will conclude by determining the resulting scope of preemption which is on my view not without substantial limitations.