Last year the Brady group claimed that they had "saved" over 2 million people from guns, due to initial denials on the background checks.
When you look a little closer at the facts, it turns out of those 2 million over 95% were false denials with a wrong name of incorrect address. But that's still 100,00 people that were denied for a reason. I don't know about other districts, but in the Midwest a grand total of only 30 people were prosecuted for trying to buy a gun illegally. That's a pathetic level of enforcement.
In crime ridden Chicago (498 shot in 2015), gun charges are the first to be plead away by the States Attorney. The three Gang members that shot and killed 15 year old Hadiya Pendleton last year were out of jail after their 3rd gun possession charge had been plead down to a misdemeanor charge. How many things are wrong with that sentence? Three guys with multiple gun charges keep getting out and getting their hands on new guns. And Illinois has all the laws the President wants already on the books including Universal Background Checks for private sales.
You'll never stop all the "bad people from using guns" but not pleading down gun charges, keeping them locked up as a serious deterrent and getting serious about prosecuting straw purchasers might help.
It's going to be a lot more effective than more "Gun Free Zone" signs.