Gee, good thing they have strict gun laws in Belgium.
Guns aren't a top issue of mine, but I figure the 2A sites are going to be pointing that out. The laws don't move the dial much on the crime rate, whether they are strict or loose. John Lott claims that concealed carry reduces the crime rate, opponents claim his research is flawed. I'm nothing of an expert on that kind of research, so I couldn't say. But the contrary research is also undramatic. Enough so so that any study that does yield dramatic results either way should be viewed with immediate suspicion.
Violent crime is cultural, and perhaps even has some genetic underpinnings. I suspect, from listening to them, that the gun control folks - we have a lot in mental health - believe that just generally discouraging anyone they talk to from liking guns will turn the tide.
Similarly, sex education. Whether a district has nothing, abstinence only, or daily condom-on-bananas openness doesn't seem to change teenage behavior more than a bit, and that's temporary. Ditto drug education. It's been that way for years.