If it is in the Civil Law, it would be constitutional.
If it is intended to regulate how the Commander in Chief exercises his authority to use Military Force or defend the country, it would be unconstitutional.
Note that the President takes an oath to defend the country, the congress does not.
Information gathered would not be admissible in civil court, but could be used in a Military Commission.
Spies and saboteurs (unlawful enemy combatants) can be tried by Military Commission whether a citizen or not.
You mean alleged spies and saboteurs. And that means the military gets to decide whether or not these people fall under military jurisdiction. That effectively places them over the civil jurisdiction.