There are many reasons for Congress to consider legislation. One of the primary reasons for Congress to consider legislation is that it believes that the judiciary will not find the subject matter of the statute already protected by the Constitution.
Last Thursday, Lame Duck Virginia Senator George Allen proposed SB 4057, tentatively titled The National Park Second Amendment Restoration and Personal Protection Act of 2006. According to the current description of the bill, it would "protect the second amendment rights of individuals to carry firearms in units of the National Park System." If passed, it would permit a properly licensed individual to carry a concealed weapon in a National Park.
Of course, the bill's title and short description do nothing other than to obscure the bill's point and confuse debate. The Second Amendment doesn't grant you the right to carry a concealed weapon in the National Park System. That's why you're proposing this law.