On February 20, 2013, you wrote to John Brennan requesting additional information concerning the Administration's views about whether "the President has the power to authorize lethal force, such as drone strike, against a U.S. citizen on U.S. soil, and without trial."
As members of this administration have previously indicated, the US government has not carried out drone strikes in the United States and has no intention of doing so. As a policy matter moreover, we reject the use of military force where well-established law enforcement authorities in this country provide the best means for incapacitating a terrorist threat. We have a long history of using the criminal justice system to incapacitate individuals located in our country who pose a threat to the United States and its interests abroad. Hundreds of individuals have been arrested and convicted of terrorism-related offenses in our federal courts.
The question you have posed is therefore entirely hypothetical, unlikely to occur, and one we hope no president will ever have to confront. It is possible, I suppose, to imagine an extraordinary circumstance in which it would be necessary and appropriate under the Constitution and applicable laws of the United States for the President to authorize the military to use lethal force within the territory of the United States. For example, the president could conceivably have no choice but to authorize the military to use such force if necessary to protect the homeland in the circumstances like a catastrophic attack like the ones suffered on December 7, 1941, and September 11, 2001.
Were such an emergency to arise, I would examine the particular facts and circumstances before advising the President on the scope of his authority.
There's more to the following statement than appears at first blush:
As a policy matter moreover, we reject the use of military force where well-established law enforcement authorities in this country provide the best means for incapacitating a terrorist threat.
Specifically, Holder did not say "we are legally constrained by the Constitution from depriving people of life, liberty or property without due process of law, and from using military force on U.S. soil". Instead, he said that the Obama administration was so far abstaining from using a power it already has as a current "policy" decision.
John Glaser notes:
The concluding legal opinion represents a radical betrayal of constitutional limits imposed on the state for depriving citizens of life, liberty and property. Officially now, Obama's kingly authority to play Judge, Jury, and Executioner and deprive Americans of their life without due process of law applies not only to Americans abroad but to citizens that are inside the United States.
"The US Attorney General's refusal to rule out the possibility of drone strikes on American citizens and on American soil is more than frightening -- it is an affront the Constitutional due process rights of all Americans," Sen. Paul said in a statement.
Holder, along with the Obama administration, is making it seem as if the President's use of lethal force, as in the drone war, would only be used in circumstances like another impending 9/11 attack or something. Only when an attack is imminent.
But that categorical limitation on the President's authority to kill depends upon their definition of "imminence," which we learned from a leaked Justice Department white paper last month, is extremely broad.
The memo refers to what it calls a "broader concept of imminence" than what has traditionally been required, like actual intelligence of an ongoing plot against the US.
"The condition that an operational leader present an "imminent' threat of violent attack against the United States does not require the United States to have clear evidence that a specific attack on U.S. persons and interests will take place in the immediate future," the memo states, contradicting conventional international law.