If Gadahn is not at least charged with treason, I think we can assume that Obama and Holder do not believe that treason against the United States exists as an offense anymore.
In October 2006, he was indicted in a US federal court under charges of treason and providing material support to a foreign terrorist organization for making al Qaeda propaganda videos. "By aligning himself with al Qaeda, by moving overseas to be closer to al Qaeda’s base and leadership, and by joining in advocating al Qaeda’s terrorist agenda, an agenda that includes the overthrow of the United States government and the murder of American citizens, Adam Gadahn has committed treason against the United States of America," said US Attorney Debra Wong Yang. He is the first American to be indicted for treason since 1952.
Read more: http://www.longwarjournal.org/archives/2010/03/american_al_qaeda_sp.php#ixzz0hWeiYsDC