A case from a "sister circuit" will be treated as "persuasive authority", but not precedent. Such a case can be used in argument, and the court will give it deferential treatment, and may follow it. But it cannot be relied upon as determinative. Really, though, nothing in the federal courts can be relied upon as determinative in my estimation.
That said, I'll point out that the Fourth Circuit is rabid about protecting what they see as the necessary power of the State as implemented in the decisions of just plain cops. So much so, that they don't seem to realize that their policies are most likely to undermine the legitimate authority that cops have, and alienate the citizens, creating hostility that would not otherwise exist. They bend over so far backward to protect the bone-headed decisions of individual cops, that they have created a climate in which, as a civil matter, cops are pretty much not responsible for anything. I don't bring actions based on 42 U.S.C. 1983 for just that reason. There's really no point, and even if I were being paid by the hour, I wouldn't take the case because, like I told Diane Nelson back in ninth grade when she expressed an interest in a relationship, I'd only be taking advantage for selfish reasons. (I am preparing three different suits against law enforcement officers at present, however, to be brought in Virginia courts on the basis of Virginia law.)
Back to the "qualified immunity" issue: the principle holds that a cop who is reasonably informed as to the state of the law, and acts on the basis of his good-faith understanding of the law, will be given the benefit of the doubt and granted civil immunity, even if he was wrong in his understanding. I'm thinking now of Aaron Stevenson, who you may remember, was the subject of an illegal arrest, false imprisonment, and a gun confiscation in the City of Roanoke a while back. The Fourth Circuit said, in effect, that the cops were just a couple of good ol' boys who were bass-ackwards in their thinking, but doing the best they could, and they didn't know what they were doing was illegal. Everyone else would be told, "you are presumed to know what the law is.", but not these boys. The qualification for qualified immunity in the Fourth Circuit is the requirement that one actually be a law enforcement officer.
I hope I don't sound cynical. I also hope that certain judges will wake up and remember why we have a legal system before civilization is gone from Virginia, as it already is in so many other parts of the formerly civilized world. (I don't include Maryland in that, since Maryland was never civilized. Part of the problem with the Fourth Circuit is that Maryland is in it, too.)