hwydopehound, I dont know if you're confusing my response with sonicwaste's that i quoted, but you basically echoed what i said about a K-9 being called and it not being needed to be torn for the k-9 to smell whats in the package.
The USPS, is under federal jurisdiction and therefore a search warrant for MAIL will not vary from state to state. If a dog alerts ON MAIL, (PC now exists and thus the reason that a search warrant can even be obtained) a search warrant MUST be obtained before the package is opened. This will NEVER vary.
Of course in other Probable cause scenarios, regarding houses and vehicles, yes that will vary from state to state. A dog alerts to a vehicle in NC, probable cause-search entire vehicle without a warrant (vehicle exception rule). A dog alerts on a vehicle in PA- search warrant must be obtained b4 searching the vehicle. Lets not get off topic though.