In the state of New Mexico, businesses can prohibit firearms on their premises, concealed permit notwithstanding. They're required to erect signage of a minimum size stating the business is a gun-free zone. For the most part, all hospitals, churches, movies houses, clinics, Walmarts, Targets, grocery stores, and most small businesses are posted as gun-free. Great! But if I were a terrorist, guess where I'd go to shoot a few citizens?
By law, any establishment which serves liquor, and all schools, must be a gun-free zone, replete with state-issued signage. Only problem is, the signage is much smaller in physical size than the required ones mentioned above! But this leads to an interesting question. If a business (or school district) can opt in to a gun-free zone, why can't a business (or school) opt out?