In this case, I would think that they had no probable cause to have a dog sniff the car even if the dog was already present at the scene. Unless the driver gave some clear indication that led the officers to reasonably believe that he had illegal drugs in his car, any search, including sniffing by a police dog would be an unreasonable violation of the 4th amendment.
They called in the dogs on a hunch. They need a lot more than that.
Read the decision, it is pretty short. He wasn’t waiting for a dog as the headline suggests, he was waiting for a backup officer because there were two men in the car, and he feared a positive alert would be met with an attempt to escape.
He did establish what he, and Thomas/Alito thought was reasonable suspicion after stopping the guys, strong masking odor, excessive nervousness, and a suspect story by both, which is all that is required to detain someone for investigation of criminal activity.
It looks like the reasonable suspicion was tossed by an appeals judge and not argued, so I suppose this could be back to determine if the courts accept the facts supporting reasonable suspicion.