Given Heien’s distinction between the standard under the Fourth Amendment and the standard for qualified immunity, we are left after Heien with the conclusion that the concept of “objectively reasonable” conduct varies depending on the type of claim the Court is addressing. In particular, Heien leaves open both the question of what constitutes a reasonable mistake of law for Fourth Amendment purposes and the question of how that answer relates to the good faith exception to the exclusionary rule. This Article explores these questions. Part I examines how the Court has increased its tolerance of police mistakes, both in addressing Fourth Amendment claims and in the remedial doctrines of qualified immunity and the good faith exception to the exclusionary rule, and it ends with an examination of the Heien decision. Part II reviews and evaluates the lower courts’ application of Heien from December 2014 through December 2015 on both the substantive Fourth Amendment claims and the good faith exception. This review concludes that while many courts are showing too much deference to police error on substantive Fourth Amendment claims, they also are correctly not considering the good faith exception once they conclude that there was an unreasonable mistake of law by the police. In short, an unreasonable mistake of law renders the good faith exception not applicable. Part III considers the implications of this conclusion for the good faith exception to the exclusionary rule and concludes that Heien—a decision that expands toleration of police error—could also paradoxically provide a possible limiting principle to the expansive language that the Court has used in its most recent good faith exception cases.