"It also bans... training and testing" It also is a big part of that sentence. Reading through the paragraph: first two sentences of paragraph:

Shortly before the inspector general report was completed a year ago, the Pentagon issued a new policy governing the use of spy drones. It requires the defense secretary to approve all domestic spy drone operations.* It says that unless permitted by law and approved by the secretary, drones "may not conduct surveillance on U.S. persons."

So at this point, drones are allowed to do spying operations on us citizens in the us if approved by the defense secretary and permitted by the law. At this point, armed or unarmed has not been specified, so we are talking about both at this point in the paragraph.

Last sentence of paragraph:

It also bans the use of armed drones over the United States for anything other than training and testing.

This now means that all drones must be approved by the defense secretary and permitted by the law to do surveillance missions, and that armed drones are completely restricted to training and testing. Unarmed drones can do spying missions if the above requirements are met, but armed drones can only be used for training and testing in the us.

Since armed drones are restricted to these two purposes, the writer must be discussing unarmed drones the entire time that they're stating the requirements for spying on US citizens with drones in the US; because, if they're spying on us citizens with drones in the US, they aren't training or testing, and therefore can not be armed - making them unarmed.

If i'm being unclear please notify me. The wording got a bit extreme in the last paragraph.