I see. And what makes your interpretation of what's Constitutional, what is actually required of Congress in it's power to declare war, more valid than that of folk like Jefferson, Washington (called out of retirement to command our armed forces during the Quasi War), Madison, Monroe, and Hamilton?
Consider: The Constitution spells out the actual text of the Presidential Oath of Office. Those exact words are to be used to swear in a new President. It does not, however, specify what form a declaration of war must take. There's no "before a war may be declared, Congress will vote on the following statement [text of wording of declaration of war]" paralleling that of the Presidential oath of office. Nope. Since it's not defined in the Constitution, by default it's left to Congress to decide what form constitutes a declaration of war. On what basis is something like "Congress authorizes the President to begin military operations against the nation of France in response to seizure of American ships by warships of the French Navy" (one of the main causes of the quasi-war with France) not qualify if Congress decides that it is sufficient?
Now, as for the claim that Congress has passed Unconstitutional laws from the beginning, consider the situation. Piracy suppression has been a function of the Navy since there was a Navy, and that is before the Constitution was written. Piracy Suppression involves using military force against foreign (often) nationals based out of foreign (often) ports. (That some pirates may have been US Nationals operating out of US ports doesn't change that anti-pirate operations were carried out against foreign nationals on foreign--if any--flag vessels, sailing out of foreign ports.) Piracy suppression was going on before the Constitution was written. It was going on while the Constitution was being written and debated. It was going on while the Constitution was being ratified. And it continued after the Constitution was ratified. Now, if the Congressional power to declare war was actually intended to prevent any use of military power outside the US (we'll leave aside the question of inside since Posse Commitatus was still pretty far in the future), we have here an example of the US Navy doing something before the Constitution was written that this clause was supposed to forbid, then continuing it after the Constitution was ratified . . . and nobody said anything?
If the provision that Congress is the branch that declares war was really to prevent use of military force without Congress saying "a state of war exists between..." then shouldn't something have been said when Commodore David Porter went out with 20 gunboats in an effort to suppress piracy (given that task by Thomas Jefferson)?
I mean, the Louisiana Purchase was strictly speaking unconstitutional and, in fact, Jefferson himself questioned the constitutionality of it--and did it anyway. But the point is the question was raised. The Constitutionality was questioned.
Where are the questions, before the modern era, of folk questioning the idea that not all uses of military force by the United States require a formal declaration if war using language something like "declare that a state of war exists between the US and..."?
The military is completely free to investigate and he is required to testify in any case just the same as the rest of us. He is not exempt from this. He must comply without question during a court martial because you can't plead the fifth in the military, right? 
