Yes, people can still buy them illegally, but crime overall decreases because access is made much more difficult.
Crime will happen with or without the sale of weapons. One argument against would be that people would be defenseless against criminals that manage to get hands on their weapons, but for every civilian that manages to defuse a criminal with their own weapon there are dozens of persons killed by either someone who got their weapon legally (I highly doubt that the person in Colorado would have been able to get such high caliber rifles if they were restricted, I mean, you can get things like M16 legally in some states) or accidental deaths. And intelligent criminals do know they can politely ask for the weapons of the persons they are robbing too for that matter.
Of course, the US have a problem in having a ground border with Mexico, but then again, a lot of the weapons the gangs there use also come from the US - good old Texas anyone?
I agree with you that persons are a problem, but I blame the American government and society for that. Freedom of economy and little government intervention created a society that does not cater to the needs of their own poor, unlike in Europe, Canada and East Asia. It is the only developed country without public health care.
Recette - Witch 400 | EmiriTachibana - Diva 400 | SakuraHiiragi - Champion 35x | AnaJessicaAyano - Soul Master 26x | LeslieSun - Witch 26x
Bye Bright Shadow Japan, I will miss you all and my bunch of characters very much ~~