You say that:
1. The authority is specific and narrowly constrained.
Laws written by Congress do not override the Constitution, if they wish to change the Constitution they need to follow Article V. Regardless we can all site examples of laws that were “specific and narrowly constrained” that were violated by the Executive or broadened by the Courts.
2. The battlefield is wherever the enemy is.
Since they have declared the whole world to be the battlefield including the United States, when can we expect Martial Law to be declared?
3. The Fifth Amendment does not apply to unprivileged belligerents.
On American soil who determines the definition of belligerents, Congress, the President, the Military or the Courts?
Abraham Lincoln detained without habeas corpus over 13,000 citizens that disagreed with his polices including a US Representative. After the war, the Supreme Court officially restored habeas corpus, ruling that military trials in areas where the civil courts were capable of functioning were illegal.
Woodrow Wilson again detained American citizens that spoke out against his policies during WWI or just happened to speak German in public.
And the most outrageous of all was FDR’s confining American citizens to Internment Camps without charges just because they were of Japanese descent.Details