Criminal is an Arbitrary Label
Both advocates of gun control and gun rights spend a lot of time discussing the need to keep guns out of the hands of criminals. On paper it sounds like a good idea but when you look at what the label "criminal" means in American society it becomes a less desirable idea.
What is a criminal? Criminal, in our society, is a completely arbitrary label. If a select group of individuals gather in a designated marble building, write some words on pieces of paper, and a majority of them later vote to make those words law then anybody in violation of those words is no a criminal.
Imagine that today, March 7th, Mr. Smith is an upstanding law-abiding citizen. Tomorrow some guys donning suits and gathering in a marble building write some words that Mr. Smith is in violation of and vote to make it law. By March 9th Mr. Smith is no longer a law-abiding citizen but a wanted criminal.
This is why I have no time for programs that are supposedly meant to keep guns out of the hands of criminals. Until we redefine criminal to actually mean something other than arbitrarily selected individuals the mission of keeping anything from the hands of criminals is foolhardy. Instead we should first work to make the process of defining who is and isn't a criminal something consistent and predictable instead of arbitrary. Once that has been done we can have a discussion about keeping guns out of the hands of criminals.