I’d argue they could pass a law any time that gives details on when and how soldiers are to be quartered in times of war.
But to remain constitutional, it would need to only be effective when in time of war. Which immediately raises the question of what sort of conflict is the “war” that word is referring to.
In the OP, I said that Slovik “basically goaded his commanders and military judges into executing him.” There is some hyperbole there, but not much. Slovik took the fact that no other deserters had been executed as evidence of the fact that it could not happen to him.
The difference is that the others who were charged claimed some extenuating circumstance. Slovik pointedly did not do this until it was far too late.
Instead he wrote in a signed statement: “I, Pvt. Eddie D. Slovik, 36896415, confess to the desertion of the United States Army.”
What kind of idiot confesses to a capital crime in a signed statement? And when he is told was the consequences will be refuses to back down?