.... But this too fails to appreciate its application in the field, where police have become, at least in their own minds, the arbiters of law at the end of a gun.

The Supreme Court has now held that they are, indeed, the arbiters of the law, with the only condition being that they can craft a half-baked, phony, facile excuse for why they got the law wrong.  The new test for "reasonableness" under the Fourth Amendment is how good a spin the prosecution and cops can offer for mistakes.  As it turns out, this is the one thing that they're exceptionally good at.  The black letter law of Fourth Amendment is now "close enough."