In a decision on December 29, 2021, the Pennsylvania Supreme Court held that the odor of cannabis (marijuana or hemp) alone would not justify the warrantless search of a vehicle.  They did leave open the  possibility that odor of marijuana plus other factors might provide probable cause for a warrantless search.  

A Pennsylvania trooper stopped a vehicle after observing speeding and a failure to stop at a stop sign.  During the stop, the trooper smelled the odor of burnt marijuana.  The trooper invoked the smell of marijuana and advised the occupants that he would be searching the vehicle.  Two of the three occupants of the vehicle then provided their medical marijuana cards which authorized them to possess and consume medical marijuana in Pennsylvania.  

The two troopers who were present testified that they were unsure how a medical marijuana patient was permitted to ingest the product or that the person could possess green leafy material marijuana.  The troopers also believed that THC vapes would have no odor.  

The troopers proceeded with the warrantless vehicle search.  They found small amounts of "shake" in the floorboard and a Ziploc bag containing 0.79 gram of marijuana. A handgun and ammunition was also found.  

The Pennsylvania medical marijuana act does not allow for the smoking of green leafy marijuana, but it does allow that substance to be vaped.  Vaping and smoking marijuana produce the same odors.  

The Pennsylvania decision made it clear that odor of marijuana in a state where cannabis is partially legal may not be inferred as evidence of a crime and would not justify a warrantless search of a vehicle by itself.

Georgia courts have not yet fully re-examined the issue of whether the odor of cannabis justifies a warrantless search of a vehicle.  At this time, the odor of cannabis is considered sufficient to justify a warrantless search of a vehicle in Georgia.

Marijuana cards from other states do not authorize the possession or consumption of marijuana in Georgia.  Persons stopped by law enforcement in Georgia should not volunteer that they are the holders of such cards from other states.  It is evidence that the police will use as justification for a search.