When officers arrest a suspect for violating a protective order that the officers have not read and that has not in fact been violated, the arrest violates the Fourth Amendment, because probable cause cannot rest upon an officer’s misunderstanding of the law. In this civil rights suit, the Ninth Circuit held that the officers in question were not entitled to qualified immunity because their conduct so clearly violated the defendant’s Fourth Amendment rights. The plaintiff here was the subject of a protective order that prevented him from contacting his estranged wife or coming within 300 feet of her home or work place. The plaintiff showed up for services at the church he and his wife attended, and she contacted police, told them he was violating the protective order, and asked them to make an arrest. The police did not read the protective order, although the wife had a copy available, and the plaintiff’s criminal charges were eventually dismissed because the terms of the protective order did not require him to avoid his wife at the church or other public places. The Ninth Circuit rejected the argument that the information provided by the wife was a statement of a citizen informant that could be reasonably relied upon by the officers for probable cause to make an arrest, because her statements regarding the protective order were not based on observed facts but on an interpretation of the law. Officers may not justify an arrest or even a detention based on a mistake regarding the law.