Ah, c'mon Jim, you gonna make me do this.....
Police can detain and ultimately search (exception to the warrant requriement-exigent circmstance, the dope was about to drive away...) if there is reasonable suspicion to believe there is criminal activity afoot (articulable facts). There was no search inside the car until after articulable facts arose. The dog sniffed an odor outside the car. Once the dog indicated drugs, there is your articulable fact. There has long been a "plain-sniff" exception (as well as plain-view exception) to the warrant requirement as well-even though this doesn't quite apply, since the dog was sniffing outside, where it had every legal right to be.
We criminal defense law clerks discussed this at break in Con Law tonight. This is not a new infringement on the Fourth Amendment being carved out. Now get that cop for making an unecessary stop in the first place, and then we can talk Fourth Amendment violations.
Shoshana