Our Constitution gives 100% authority over ALL military matters to the Executive Branch (read: President/VP).
You know, if you're going to pose as a defender of the Constitution, it would help to know what it actually says. No, the Constitution does not grant "100% authority" over the military to the president. In fact, it would be safe to say that it doesn't grant it over anything to anyone. Look at Article I, Section 8:
The Congress shall have power...
To define and punish piracies and felonies committed on the high seas, and offenses against the law of nations;
To declare war, grant letters of marque and reprisal, and make rules concerning captures on land and water;
To raise and support armies, but no appropriation of money to that use shall be for a longer term than two years;
To provide and maintain a navy;
To make rules for the government and regulation of the land and naval forces;
To provide for calling forth the militia to execute the laws of the union, suppress insurrections and repel invasions;
To provide for organizing, arming, and disciplining, the militia, and for governing such part of them as may be employed in the service of the United States, reserving to the states respectively, the appointment of the officers, and the authority of training the militia according to the discipline prescribed by Congress;
Each of these is a military power, and each is granted to Congress. Establishing military tribunals may be a power of the president (and, I contend, in a war zone or occupied enemy territory, it is), but your initial claim, from which the rest of your argument comes, is simply false, as even a cursory reading of the Constitution shows. I'd prefer to hear about the Constitution from an admirer of communist agitators who's read it than from an administration cheerleader who hasn't.
Military trials of American soldiers are held under the UCMJ in military tribunals.
These are not the same kinds of tribunals.
Moving those foreign military trials into American civilian courts could VIOLATE our Constitution's seperation of powers by shifting said authority from the Executive Branch to the Judicial Branch.
The issue isn't tribunals outside the United States, it's tribunals inside the United States. In that case, it most certainly does not violate the Constitution to use civilian courts.
What Hentoff is arguing is to VIOLATE our Constitution to be more "fair" to foreign, anti-American terrorists - by illegally shifting authority over foreign military trials from the Executive Branch to the Judicial Branch.
Let me ask you something. What's the purpose of having any kind of trial in the first place?
Remember, we're talking about inside the United States.
Surely it's not to be fair to the guilty. It's to be fair to the innocent. You're convicting every person who'll be accused in the future without even knowing who they are, or deciding that it doesn't matter if we're fair to the innocent or not.
As Blackstone says, "It is better that ten guilty escape than one innocent suffer."
That's simply incorrect. Military tribunals are under the Executive Branch. Civilian Courts are under the Judicial Branch. Moving the trials of foreign warriors from the Executive Branch to the Judicial Branch would VIOLATE our Constitutional separation of powers.
Moreover, by attacking U.S. territory directly, foreign warriors are NOT granted more rights than if they attacked American interests abroad. The Japanese who conquered the American Aleutian islands during WW2 did not suddenly get all of the protections afforded to American citizens by our Judicial Branch courts. Likewise, foreign terrorists who attack and plan attacks against domestic American targets do not suddenly obtain the full protections of American civilian courts under our Judicial Branch. In fact, a review of my 1901 Alabama state Constitution explicitly grants the citizens of this state to unilaterly use force of arms to stop such attacks WITHOUT any trial whatsoever.
The fact that we would grant military trials at all to those who place themselves under the Geneva Convention's definition of spies and sabotuers subject to summary execution (i.e., not clothed in the military uniform of their country while planning/executing attacks), merely shows that the U.S. is extraordinarily concerned with civil rights - even to the extent that we risk damage to our nation in order to give trials to such people.