The legitimate expectation that information about perfectly lawful activity will remain private is categorically distinguishable from respondent’s hopes or expectations concerning the nondetection of contraband in the trunk of his car. A dog sniff conducted during a concededly lawful traffic stop that reveals no information other than the location of a substance that no individual has any right to possess does not violate the Fourth Amendment.And so it seems that one is entitled to privacy only if one is law abiding. Or to put it another way, if your privacy is violated and you are found to have broken a law, that's a-okay. You didn't really have the right to privacy to begin with, you dirty drug addict.
Souter and Ginsburg dissented (Rehnquist didn't participate), arguing that one must "treat a sniff as the search that it amounts to in practice." And further, Souter writes, rather poetically, "The infallible dog . . . is a creature of legal fiction."
In the past, Ginsburg has argued "Fourth Amendment protection, reserved for the innocent only, would have little force in regulating police behavior toward either the innocent or the guilty," to which I must add "um...duh."
It's just all pretty frightening and terribly depressing isn't it?