DC gun laws are in fact being straightened out under the 2nd Amendment by the courts. This has to do with checkpoint barricade at a hardened federal facility.
Washington, D.C.-— District of Columbia laws prohibits the transportation of firearms through the city unless the travel is to or from lawful recreational firearm-related activity. Firearms transported for this purpose should be carried in accordance with the general rule.
Federal Law on Transportation of Firearms
A provision of federal law serves as a defense to state or local laws which would prohibit the passage of persons with firearms in interstate travel.
Notwithstanding any state or local law, a person shall be entitled to transport a firearm from any place where he may lawfully possess and transport such firearm to any other place where he may lawfully possess and transport such firearms if the firearm is unloaded and in the trunk. In vehicles without a trunk, the unloaded firearm shall be in a locked container other than the glove compartment or console. Necessary stops, e.g., gasoline and rest, seem permissible.
Carrying on or About the Person
It must be stressed that as soon as any firearm-—handgun, rifle, or shotgun-—is carried on or about the person, or placed in a vehicle where it is readily accessible, state and local firearms laws dealing with carrying come into play. If you seek to transport firearms in such a manner, it is advisable that you determine what the law is by contacting the Attorney General’s office in each state through which you may travel or by reviewing an NRA State Firearms Law Digest. You should determine whether a permit is needed and how to obtain one if available. While many states require a permit for this type of carrying, most will not issue such permits to nonresidents and others prohibit such carrying altogether.
Transportation by Motor Vehicle: The General Rule
In most states, personally-owned firearms may be transported legally if they are unloaded, cased, and locked in the automobile trunk. As an additional precaution, firearms may be disassembled and separated from ammunition.
The exceptions to this rule deal mainly with interstate transportation of handguns. The myriad and conflicting legal requirements for firearm transportation through the states make caution the key for travelers.
If you travel with a trailer or camper that is hauled by an automobile, it is advisable to transport the firearms unloaded, cased and locked in the automobile trunk. If your vehicle is of the type in which driving and living spaces are not separated, the problem becomes one of access. If the firearm, including handguns, rifles or shotguns, is carried on or about the person, or placed in the camper where it is readily accessible to the driver or any passenger, state and local laws dealing with concealed carrying of firearms may come into play. It is suggested, therefore, that the firearm be transported unloaded, cased, and placed in a locked rear compartment of the camper or mobile home, inaccessible to the driver or passenger.
Once you reach your destination, the state or, in some areas, municipal law, will control the ownership, possession, and transportation of your firearms.
Note:Generally, when a mobile home is readily mobile, i.e., when one can simply start its engine or the engine of its towing vehicle and drive away-—even if it is capable of being used as a home-— a mobile home is considered a vehicle. If a mobile home is not mobile, i.e., it does not have an engine, or is not attached to a towing vehicle, and is on blocks, permanently connected to utilities, it is considered a house, not a vehicle.