OK you are flat out wrong. You are now moving the goal posts to make it seem the President would give an unlawful command. Of course under President Bush many unlawful commands were given and followed. So your premis is utter bull****.
I think you're missing the point that Redress et. al. are making. They're saying that the president can issue order
directly to a particular ground unit. Doing so would be a break of the chain of command.
I brought up the lawful and legal orders point, because Redress that there are no exceptions and that the president has the final say on small unit tactics. If the president is present at your piece and gives some crazy instructions to you on how to load the gun, you're not obligated to follow those instructions, if they either unsafe, violate regulations or doctrine.
Obviously, there circumstances when the chain of command can and will be broken, such as on the spot corrections for various reasons, or some sort of emergency. D-Day is a good exmaple of how the official chain of command was broken and due to throwing together ad-hoc units, because if the situtation at hand, a new un-official chain of command had to created where you might have a bird colonel leading a platoon size element and his platoon seargent is a corporal.
Ultimately, the notion of the president giving direct orders to a combat platoon, or a company is so far fetched that it's not even worth arguing about. Besides that, anyone smart enough to make it to the White House is mart enough to know that if he's every in the situation where he has to tramp through the bush with an infantry platoon that his best course of action is to keep his mouth shut and his ears open.
Proper proticol is for the president to express his intent to his chain of command and the chain of command carry out that mission, in accordance with that intent. Basically, the president tells the chain what outcome he wants and it's up to the chain to figure out how to achieve that outcome. It's silly to think that the president is going to be creating tactical doctrine right down to the company/platoon/squad level.
Can the president give the president issues orders to a small unit on the battlefield, is it leagal? Constitutionally speaking, sure. Would, or should he tell individual units what tactics to use in a firefight? Certainly not. Could he realistically get away with making such decisions? There's no way that the chain of command would stand for it. It's the reason that it's never happened before.
When the chain is broken, it will do nothing but muck up the whole system and cause a serious breakdown. My point is, if the president actually had the final say about tactics used by combat units, there are alotta elements of our military that wouldn't exist, the Training and Doctrination Command (TRADOC) would be one of them. There would be no use for corps, division, brigade and battalion commanders if it was at all proper for the president to issue orders directly to line units.
So, at the end of the day, in reality, the president doesn't have the last say on what combat tactics are to be used on the battlefield.