As of February 22, 2010, a new federal law makes possession of firearms in national parks subject to local and state firearms laws.
It is the responsibility of visitors to understand and comply with all applicable state, local, and federal firearms laws before entering this park. As a starting point, please visit the District of Columbia’s website.
See Division I, Title 7, Subtitle J, Chapter 25
See also Division IV, Title 22, Subtitle VI, Chapter 45
Federal law continues to prohibit firearms in federal facilities in this park. Those federal facilities are marked with signs at public entrances. Thus firearms are prohibited in the Thomas Jefferson Memorial.