The language in the memo is kind of ambiguous and opens the door for a LOT of abuse. Dropping the requirement that intelligence showing an immediate or ongoing threat be presented before initializing a drone strike is like saying, "We heard once that you were kind of pissed at your government and encouraged people to rise up...but we've had nothing from you in weeks. Somebody told us you were in Des Moines, so here comes a drone...just in case you're doing something so secretively that one of the best intelligence organizations in the world can't figure it out."
We've almost ALWAYS had substantial, current intelligence on enemy combatants we've attacked in war zones...intelligence that included information of imminent strikes against us or our interests or confirming involvement in a previous strike. And these people are involved in a declared war against us.
There is absolutely nothing in the memo that requires a formal declaration of war or assault against the U.S, nothing that requires a recognized act of treason. It fails to define key words in specific language that would safely and effectively limit the number of unjustified attacks against U.S. citizens and it is therefore dangerous and constitutionally unsound. By the language in this memo they could justify the killing of anybody who speaks out against the actions of the government...without charge, trial, or conviction.