Suppose that the president of the United States received intelligence that a very dangerous man was hiding in a house in a foreign country. Would it be OK for the president to get in touch with the authorities in that country and ask them to drop a bomb on that house? That's pretty much what our president did with the government of Yemen, where two attacks from the air killed dozens of people, including a number of children and possibly also including an associate of the Army psychiatrist who shot several of his comrades at Fort Hood several weeks ago. Barack Obama hasn't admitted that he OK'd the assassinations in Yemen, but his Department of Defense congratulated that nation's government on its boldness and initiative in the wake of the second attack.
Certainly, there's nothing in Article 2 of our constitution that empowers the president to engage a foreign leader (or any other foreigner) to kill one or more of his countrymen for the USA. The president does have the power to command an army and navy, but our charter is meant to refer to an American army and navy and not any foreign force. If there were a declaration of war, he might make a formal alliance that involved the application of military force by a foreign government, but there's been no such declaration, and there is no such alliance, and it would be extraordinary for a party to such an alliance to launch missiles against its own people.
If Barack Obama had no constitutional authority to order or request an attack on residents of Yemen, might he have had some moral authority to do so? He did win the Nobel peace prize, after all, an honor in which all Americans can justly bask. That prize says that all of the killing, all of the destruction, all of the displacement, all of the desecration in Iraq, Afghanistan, Panama, Yugoslavia and, yes, Vietnam, have been in the interest of peace and not motivated by hubris or arrogance or, God forbid, profit. Universally acknowledged as the world's only superpower, America has and will always have the moral authority to kill people, even children, in the interest of peace. Because we can, acting through our president, wield this awesome power, we must.
Should we be concerned that the killings in Yemen run counter to our laws? After all, when the commander-in-chief of the US armed forces "asks" you to bomb one of your neighborhoods, you would be well advised as a head of state to take that as a threat. Threatening a person to compel him to kill somebody is a felony in every state and in most foreign countries. When a government authority does it, it's a war crime. But not to worry. Government officials are above the law. Our president may be a war criminal, but his motives are as pure as his his smile is bright, and he deserves a medal for standing up to the constitution. That old thing, not near tough enough to deal with our terror-ridden times.
But if there's no law for our president and for us, what law shall we use to prosecute the Detroit bomber, who claims to have been driven to his crime by the attacks in Yemen? He would probably say, if he could, that he had as much legal right to blow up that airplane as the US and Yemeni governments had to incinerate a neighborhood. An American official plots with a Yemeni official to launch missiles on civilians (in Yemen, mind you: you'd like to think they'd send a policeman with a warrant in these parts, but who knows?). In the interests of peace, they kill some bad guys, along with many other people. In reply, and to deter further attacks, a fanatic plots with a bombmaker to kill passengers on an airliner in Detroit. Is there a legal distinction between these two plots?
There is no legal distinction, The Detroit bomber and the Washington bomber should be subjected to the same legal process. In fact, the cases should probably be tried together, since they arise out of single chain of events. But there is no case against the US president. That's because he is acting on the moral authority of the American people and not on his own account, and this places him above the law. As for the Detroit bomber, why put him on trial at all? We would just be giving him a soapbox from which to spout accusations against us, moral exemplars in a dangerous world. Why not just string him up?