Isolation and sanctions would be acts of insane stupidity at this point. Take a dodgy regime and cut them off from the international community, mess up their economy, give everyone in the country a reason to believe the world really is out to get them, and it should be no surprise when the inevitable happens: popular opinion in the country becomes increasingly paranoid, support for the dodgy regime is solidified, and the regime itself becomes more extremist and totalitarian over time. It's the perfect way to make a bad situation worse.

This might be excusable if the situation were unprecedented, but the worst part is, the pattern is not news to us at all. Cuba, North Korea, Iraq under Saddam Hussein, Iran: how many times does history have to repeat the lesson before we become willing to learn it?