No, it’s just being pragmatic.
Martial law works in a local situation, but not in a large—no, huge—piece of geography.
Take the Phillipines in WWII. While the japs held the territory, there were huge pieces of that land that were never quite held under control.
And, I really don’t think the U.S. Army would follow those rules under Obama. You are more likely to get a civil war.
Which is about the same thing.
But it couldn't happen there, either.