http://losangeles.cbslocal.com/2011/10/13/hats-off-or-get-out-valley-stores-lapd-to-ban-headgear-in-anti-crime-effort/...Under the program, a “warning notice” will be placed in the window of a business that caters to walk-in customers “to allow the customer time to remove their hat, hoodie or helmet” before entering, LAPD officials said.
If they refuse to comply, “they’d be in violation of penal code 602, which is essentially trespassing within that business,” said LAPD Capt. Justin Eisenberg....
Because robbers really care about being issued a trespassing ticket when they rob
and we dont need anyone buying hats,hoodies or helmets.
This really isn't any different from "No shirts, no shoes, no service" signs, except now businesses can call the police about it (although they likely could call the police for 'trespassing' in such a way before)