I haven't heard anyone say these were warning shots. The helicopter crews believed they were being fired upon directly, and they characterized the small arms fire as "effective." In other words, they were being hit with bullets, which probably did not succeed in penetrating the Apache armor or did minor damage.
In any event, even if these were warning shots, the decision to fire upon units of nation you are not at war with should be a decision of civilian government in any civilized society. Once you're at war, that's different. Then the military units of course must have discretion in the field. But if the civilian government doesn't have control of the military at least to the extent of being able to enforce standing orders not to fire on US units unless they are fired upon first, then there is a systemic problem in Pakistan.
I'll give you an example so you can better understand what I mean. During the Cuban Missile Crisis, the U.S. had a naval blockade to prevent Russian vessels from delivering weaponry to Cuba. The civilian government issued standing rules of engagement for U.S. navy vessels participating in the blockade. And, because they wanted to be sure that these ROE's were followed as the consquence of being trigger happy might have been global thermonuclear war, the President himself (and another time the SoD) personally telephoned the naval commander to walk him through how the confrontation was handled. In one case, a warning shot was fired without authorization and it was a "pins and needles" moment, and the military brass got chewed out for it. While that is an unusual situation where the civilian leadership has direct contact with people on the ground, the point is that decisions about whethor to fire on nations that you are not at war with is not one for military units on the ground.
If Pakistan's civilian government can't control its miltiary or its intelligence services, if they are firing on U.S. units, aiding the Taliban, looking the other way while militants sabotage our supply lines, etc. then we have a serious problem.
- wolf