As much as I detest gun control legislation, we did get some protections in the Firearms Owners Protection Act in 1986.
18 USC § 926A - Interstate transportation of firearms or The Safe Passage Provision
Notwithstanding any other provision of any law or any rule or regulation of a State or any political subdivision thereof, any person who is not otherwise prohibited by this chapter from transporting, shipping, or receiving a firearm shall be entitled to transport a firearm for any lawful purpose from any place where he may lawfully possess and carry such firearm to any other place where he may lawfully possess and carry such firearm if, during such transportation the firearm is unloaded, and neither the firearm nor any ammunition being transported is readily accessible or is directly accessible from the passenger compartment of such transporting vehicle: Provided, That in the case of a vehicle without a compartment separate from the driver’s compartment the firearm or ammunition shall be contained in a locked container other than the glove compartment or console.
ETA: All bets are off in DC. I'm as nervous as a Chihuahua trying to poop a peach pit when in Maryland. I won't carry anything firearm related into New Jersey. I've never had problems between Virginia and Florida. I do have carry permits that cover the states I travel through going south.