Orin Kerr writes:
In Florida v. Jardines (2013), the U.S. Supreme Court held that a front porch is a Fourth Amendment protected area but that there is an “implied license” allowing the police to walk up to the front door and knock in at least some cases. If the police are just coming to talk to the homeowner, the court concluded, that’s within the implied license and no Fourth Amendment search occurs. Homeowners implicitly consent to people coming to knock on the door and talk to them; that’s why they have doorbells. On the other hand, if the police are bringing a drug sniffing dog to smell for drugs, that is outside the implied license. People don’t implicitly consent to people coming to search them, and bringing a drug-sniffing dog to the front porch is a clear objective sign that the officers intend to search them. Coming to the front porch with a drug-sniffing dog is therefore a search, and the police ordinarily can’t do that without a warrant.
Now consider this question: How does Jardines apply when properties have “no trespassing” signs posted?
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