The article did mention it will require permission.
Commander-in-chiefs don't need permission; they'll pretend congress or a constitution can control them as long as it benefits them but when they really want to do something, they just go ahead and do it anyway. Heck, Lincoln was one of history's biggest offenders, nearing dictatorship levels of control, and he's revered as a hero by most. Recently, Thailand's military overthrew its gov (coup d'etat), for the 2nd time, because the military couldn't agree with the politicians actions. They don't care, if they need to take control, they will; they have the physical force to do so at any time. Only issue is that it's inefficient to operate this way; a happy citizen is a productive citizen which will yield great tax crops, but dictatorships make for very unhappy citizens and the game of confidence comes crashing down in a short time period (look at any dictatorship's economy to see how it happens: Hitler's Germany, USSR, NK, you name it.) You need the facade that government is remotely healthy for people in order for the warlords to turn a profit, and so a part of the facade is to pretend like your powers are limited.
Don't be fooled; it doesn't matter what congress says if the head the military disagrees. What is congress going to do, get its own military?