I doubt you actually have to do that. I think the cops just like it. Whether the tape gets used in court or just an investigation, there are rules here. Hank is now kind of running his own mini-DEA with no oversight, including trying to get a secret informant to record a conversation with a suspect without a warrant. I’m not a lawyer but I have a feeling Saul could get all of this thrown out of court pretty easily. I say that not as a plot point but because Hank’s obsession with catching Walt probably isn’t going to turn out so well. Hank looked like a caring hero for about 20 minutes there, but things got darker in a hurry.