Yet they say 18 USC 926a only applies when a person is CURRENTLY transporting a firearm interstate.
This is true that it does not apply in the state, but to explain it more clearly it is even worse than that. Interstate commerce makes it sound like it applies when going from one state to another, but even that is not always true.
It does not even apply to a neighboring state.
FOPA only protects you in a third state. That is the state which is not your original state, and the state that is not your "destination" state.
The firearm must be legal at the destination to even apply in a third state.
So for example if I took a road trip to New York with a pistol carried under FOPA it would not protect me from being arrested and receiving a felony under New York law for illegally possessing a firearm without a New York permit. Since it would be illegal in New York, I would also not be protected in any state in between under FOPA because the firearm in question was illegal at the intended destination.
To be protected in a third state the firearm must be legal at the destination.
If however someone was on their way to Maine from Florida, they would be protected under FOPA on the entire coast, unless they deviated from their path, at which point the state they deviated in would be counted as a "destination". So if they took a break to see the sites in D.C. or New York City, or just had to stop and see where the first shots that lead to the United States were fired at Lexington (anti-gun MA) then they would not be covered.
Those locations would become "destinations" and so the gun would go from legal to illegal, even though it was still being transported in the method described by FOPA.
Stopping to see symbols of freedom like say the Statue of Liberty could result in a valid felony charge, stripping you of your freedoms (because just possession is a felony, even if it is locked in your trunk unloaded and in compliance with FOPA.)
Most states are less restrictive than the requirements under FOPA anyways. (Even California is less restrictive than the requirements under FOPA.)
A few are not.