Indeed, if Friedersdorf is correct, Abraham Lincoln erred when he resisted the South's effort to secede in 1861. That is, under Friedersdorf's logic, Lincoln should have abjured military force against the Southern rebellion and instead sought indictments against the 10s of thousands of Confederate soldiers --- all American citizens according to Lincoln --- who had taken arms against the union and, I suppose, asked them to turn themselves in. Fortunately Lincoln took a different approach.
3. The Congress of the United States apparently has a different view of International Law. On September 18, 2011 it passed the Authorization for use of Military Force, empowering the President to employ military force against Al Qaeda and those who support it. The AUMF contains no limitation on where the President may employ such force. Nor does it purport to prevent the President from using such force outside "armed conflict zones." Congress passed the AUMF after observing the consequences of taking an ACLU-like "law enforcement" approach to Al Qaeda, even after that organization had committed several acts of War against the United States, including the 1993 bombing of the World Trade Center and expressly declared war against the United States in 1998. (See The Report of the 9-11 Commission, beginning on page 47; id. at 59-62 ("War on the United States 1992-1996")). The 1998 Grand Jury indictment of Bin Laden can be found here. The indictment was apparently ineffective.
4. Even if a treaty or other rule of international law purported to implement the approach sought by the ACLU, Congress could, if it wished, abrogate that rule as a matter of domestic Constitutional Law. That is, the Supreme Court has repeated recognized the so-called "last in time rule," under which a statute trumps a previously-passed treaty. As between the AUMF and any purported rule of international law, then, the AUMF, which expressly authorizes the unrestricted use of military force against Al Qaeda, would prevail.
5. The rule proposed by Friedersdorf and ACLU would produce odd results, to say the least. Imagine, for instance, if Al Qaeda were to take over Iran and move thousands of fighters there. The country would not be a "zone of armed conflict." Thus, under the Friedersdorf/ACLU approach, America and her allies would have to stand idly by and do nothing as this enemy gained strength. (The only exception, according to the ACLU, would be for an imminent threat; one suspects that the victims of such a "threat" would only become aware of it after it was too late.) Of course, the United States could issue a warrant for the arrest of various members of Al Qaeda, but one doubts that those indicted would surrender themselves to U.S. authorities or that the FBI could serve such warrants without great risk.
6. Indeed, the Friedersdorf/ACLU logic calls into question the recent raid that killed Osama Bin Laden, to say the least. The sleepy suburb of Abbottabad, Pakistan is no more a "zone of armed conflict" than is Yemen --- the suspected whereabouts of Anwar al-Awaki. Nor did Bin Laden on May 1 pose any qreater threat to the United States than Anwar al-Awaki. According to the ACLU, however, the United States cannot use military force against citizens or non-citizens outside a zone of armed conflict. We should all look forward to the ACLU's effort to explain its views on the legality of the recent raid in Abbottabad and how, absent such a raid, we could have eliminated Mr. Bin Laden.
7. Finally, it should be noted that Friedersdorf relies on two make weight arguments designed to make his position apparently stronger than it really is. First, he frames his argument around the President's effort to attack American citizens. However, the arguments he derives from international law apply with equal force to attacks on citizens and non-citizens alike. Second, Friedersdorf decries the "secrecy" of President Obama's order. At the same time, one doubts that Friedersdorf and others opposed to President Obama's order would feel better if the order were published in the New York Times. "At bottom" Friedersdorf is apparently arguing that, American citizen or not, an enemy's presence outside a zone of armed conflict should immunize him or her from military action, until of course that enemy chooses, at his leisure, to attack us.