Immediately after the "Montreal Massacre" (6 Dec 1989) a politician said something true. Then Minister of Justice for Canada was asked if he was going to tighten up gun laws in Canada while on news camera... The cops were still picking up brass at the university... His response included "You can't legislate sanity."
He was replaced within two days by a new minister who did enact new firearms law.
You can't legislate sanity.
Interesting article in the December 2012 issue of the Atlantic "The Case for More Guns" by Jeffrey Goldberg.
In the same sense "You can't legislate against sickness", or even "You can't legislate immortality". That doesn't mean that societies should not care for the ill, or throw the elderly onto the streets.