Do "No Trespassing" signs make a warrantless knock-and-talk unconstitutional?

United States v. Carloss, No. 13-7082 (10th Cir. Mar. 11, 2016).

The Supreme Court has said that the police, without a warrant, may enter your property, knock on your door, and ask to talk to you. You don’t have to speak with them, and you can ask them to leave—but the mere act of knocking and talking can be done without a warrant. 

But what if—as in this case—the homeowner has a sign in the yard that reads, “No Trespassing”? That sign by itself generally isn’t enough to tell a reasonable officer he can’t enter the premises, a majority of this Tenth Circuit panel holds. And here, in fact, there’s testimony that the sign was put up to discourage drunks from wandering onto the property—not to keep all visitors away.

Now, there was also a sign on the front door telling visitors that “Hunting, Fishing, Trapping or Trespassing for Any Purpose is Strictly Forbidden.” The majority believes, though, that this sign didn’t make things any clearer. Mostly it just told people not to exploit the property without permission. Because the police had an implied license to enter the property and knock on the door, the knock-and-talk that led to the defendant’s conviction didn’t violate the Fourth Amendment.

Judge Tymkovich writes a concurrence to make clear his view that a no-trespassing sign, in certain circumstances, could revoke the police’s implicit license to enter and knock. But, he argues, the sign here didn’t do that.

Judge Gorsuch issues a characteristically readable dissent, objecting that the majority has decided the case on a ground that the parties didn’t argue and the district court didn’t reach. He also argues that even if the first no-trespassing sign wasn’t enough to warn the police off the property, the sign on the door should have—particularly by forbidding “trespassing for any purpose.”