Gene Thornton, "Militia," as described by the Militia Act of 1903, is used to describe two groups.  Organized militia consists of State militia forces, notably, the National Guard and Naval Militia.  Unorganized militia consists of every able-bodied man of at least 17 and under 45 years of age who is not a member of the National Guard or Naval Militia.  The Second Amendment grants the right of gun ownership to members of a "well regulated militia" -- the organized militia -- not the unorganized militia.