Even al-Qaida gloats about what's possible under U.S. gun laws. In June 2011, a senior al-Qaida operative, Adam Gadahn, released a video message rallying people to take advantage of opportunities those laws provide.
"America is absolutely awash with easily obtainable firearms," Gadahn says, explaining that "you can go down to a gun show at the local convention center" and buy a gun without a background check.
Then a faint smile crosses Gadahn's face. "So what are you waiting for?" he asks.