A few notes about Firearms Owner Protection Act (FOPA) (cited above) and Maryland law.
Maryland law only permits owners to transport a firearm in a vehicle for a handful of enumerated reasons (such as to go from the home to the gun range (see below)). Going to another state, in general, is not one of those reasons. Years ago, I contacted the Maryland Attorney General's Office and inquired if transporting a firearm from my home in Maryland to Virginia would be covered under FOPA, and therefore protected by the federal statute. The response came back that FOPA did not apply unless you had a carry permit in Maryland. The attorney interpreted the term "lawfully possess and carry" to mean that the person must have a carry permit in both originating state, and destination state. I pointed out that I can "possess and carry" on my own property, and the attorney indicated that it was not how the state read the statute.
I understand that the State Police have now officially acknowledges FOPA coverage for people in our situation, but it is not a "slam dunk" given historically inconsistent interpretations by the state.
Maryland statute:
Criminal Law § 4-203. Wearing, carrying, or transporting handgun (a) Prohibited. --
(1) Except as provided in subsection (b) of this section, a person may not:
(i) wear, carry, or transport a handgun, whether concealed or open, on or about the person;
(ii) wear, carry, or knowingly transport a handgun, whether concealed or open, in a vehicle traveling on a
road or parking lot generally used by the public, highway, waterway, or airway of the State;
(b) Exceptions. -- This section does not prohibit:
(3) the carrying of a handgun on the person or in a vehicle while the person is transporting the handgun to or from the place of legal purchase or sale, or to or from a bona fide repair shop, or between bona fide residences of the person, or between the bona fide residence and place of business of the person, if the business is operated and owned substantially by the person if each handgun is unloaded and carried in an enclosed case or an enclosed holster;
(4) the wearing, carrying, or transporting by a person of a handgun used in connection with an organized military activity, a target shoot, formal or informal target practice, sport shooting event, hunting, a Department of Natural Resources-sponsored firearms and hunter safety class, trapping, or a dog obedience training class or show, while the person is engaged in, on the way to, or returning from that activity if each handgun is unloaded and carried in an enclosed case or an enclosed holster;
(5) the moving by a bona fide gun collector of part or all of the collector's gun collection from place to place for public or private exhibition if each handgun is unloaded and carried in an enclosed case or an enclosed holster;
(6) the wearing, carrying, or transporting of a handgun by a person on real estate that the person owns or leases or where the person resides or within the confines of a business establishment that the person owns or leases;