If I'm not mistaken, wasn't Kentucky v King about police-created exigency?
The defense's argument was that the evidence should be supressed, because the police knocked on the door, and that they created exigency.
The supremes ruled that a police officer knocking on a door is reasonable, and the police don't create their own exigency when they do that.
You're right that SCOTUS sets binding case law for the entire country, but case law out of other districts is legal precedence, and considered persuasive when deciding subsequent cases with similar issues or facts.
Unless the district you're in has already made a binding ruling, legal precedence very much comes into play.
We have to deal with it all the time.
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