The possibility of getting unintentionally swept up by Maryland State Police for a gun violation is a LOT worse than your last alert portrayed.
Maryland does not honor concealed carry permits from other states. The Maryland State Police vehicles have their on-board computer connected to the automatic license plate readers in their patrol cars. These computers are set to flag the patrolman of out-of-state vehicles with owners that have concealed carry permits. With state sharing all this information in electronic data bases, the "hits" are found almost instantaneously.
The patrolman can elect to stop the vehicle and challenge the driver to produce his concealed weapon, for which he has a legal permit IN ANOTHER STATE. If the driver is found to have a concealed firearm (handgun), he has violated Maryland State firearms law. The person will be arrested and there is a three year minimum sentence.
Having a concealed carry permit in another state may be probable cause for the patrolman to do a search of the out-of-state vehicle. I've seen this done along the Route 50 stretch between Annapolis and Ocean City, some poor sap with the contents of his vehicle splayed on the ground while the officer searched for an "illegal" hand gun, for which the individual had a legal permit to carry in another state.
The bottom line: IF YOU ARE LEGALLY CARRYING CONCEALED FROM ANOTHER STATE, DO NOT EVEN DRIVE THROUGH MARYLAND. AND IF YOU HAVE A PERMIT FROM ANOTHER STATE, EVEN IF YOU ARE NOT CARRYING, EXPECT TO BE STOPPED. According to one Maryland attorney specializing in criminal law, roughly 19 out of 20 of his unlawful gun transportation clients are not from the State of Maryland (https://criminallawyermaryland.net/maryland-gun-lawyer/transporting/ )
I cannot speak to the veracity of the claim, however, former Virginia Governor McAullife vetoed a bill that would have stopped the sharing of VA CHP information with oppressive states like Maryland. I can say from personal experience, the above warning is fair and should be heeded. I have been subjected to a pat down on the shoulder of the highway by law enforcement when returning from a pistol match. The hassle in that case came not from a State Trooper, but from the MD Transit Authority, a group that is well-known for their proclivity for harassing travelers. Although the firearms were being legally transported, "for the safety of the public" my companion and I were detained and patted down (after the scared cop called for backup) during a traffic stop; a stop that we soon found out was made for no legitimate reason.
When I travel to and from matches in Maryland, my firearm and ammo are in separate, and locked, containers. The containers are placed in the trunk or cargo area. I drive with an acute awareness of the speed limit. A copy of U.S.C. Title 18, §926A is within reach. I make doubly sure I have no loose rounds left in my range bag or pockets for the drive home. The purposeful harassment has only happened once, but I prepare and accept that it's always a distinct possibility.
When I travel to visit family, I simply succumb to the loss of my rights and leave my firearm at home. I then rely solely on wits, observation, and other legal defensive tools.