Brother, where have you been?There is no case law I am aware of that limits stops in any way.
There have been major cases in IL, MD, NJ, NY, and MA regarding what constitutes travel status.
After the US AG under Bush sent out a policy letter, IL backed off on grabbing people at airports, but NY and NJ have not agreed to follow the Fed FOPA at all. There is still an open lawsuit about a UT man arrested in NJ because his plane was diverted from Philly.
While I was in MD, a group was arrested at a motel near me for staying the night in MD with guns in the trunk. The motel personnel turned them in. You can transport a firearm in MD only between specific locations, which makes it impossible to legally play tourist in MD with a gun anywhere in the car.
Based on the different interpretation of FOPA by various states, and the ones that just ignore it, it is vital to be fully knowledgeable of each state's law and policies when visiting.
You are on firm ground only if you are following the laws where you are. No other state gives a flip about your home state's laws. FOPA only covers an empty gun locked away while traveling between two legal locations.