I think the answer there is to stop visiting national parks till the allow guns.
This was for the educational benefit of the rest of us, the two young women in question were too much of the tree-hugging kind to buy a gun.
This guys MO points out one thing- gun bans only create protection free zones for predators to roam, they don't protect anyone.
One thing I wish gun rights lawyers would try to do in a case like this, where people are killed in a area of a local gun ban, is to sue the government for failure to protect.
Now normally you cannot sue the government for them failing to protect a individual. However, there is a escape clause. If a special situation existed where the deceased was PROMISED protection, or led to believe that he would be individually protected, then you can sue the police agency involved.
What I would like to see is somone sue on the grounds that special area gun bans, like for national parks, and for schools, hospitals, churches, ect. DO create such a special situation where the government agency that imposed the ban now IS responsible for the safety of everyone within that area, and can be held liable.
The same thing with private companies that take it upon themselves to ban firearms from their property. They are then liable for assaults and homocides that take place on their posted property.
As far as I can tell, no one has ever tried to approach this issue from this angle.