Yes, of course they can eventually, if we don't take a number of precautions, mainly securing fissile material and tactical nuclear weapons in the former soviet union. But it is highly unlikely that Al-Qaeda has a working nuclear device right now. A radiological device, perhaps. And the delivery method would more likely be a shipping container than through the border. Just trying to get the facts straight.
I'm more worried about north korea or pakistan supplying them than Russian stuff.
Either way though, it's all but inevitable. And your little dreams of worrying about their civil rights will vanish up along with hundreds of thousands of infidels.