Yeah, Eegore and Mark are correct, the president has responsibilities and powers, that put in in a position, in a sense, be above the law....
Much in the same simplistic explanation the Head Chef, has final say, what leaves the kitchen, perhaps having to "override" the recipe, because of obstacles that arrived in the preparations of the meal..... ( yeah...pretty simple comparison...
)
It was not meant to be a legislating (political) tool for the opposition, much has been written as to why.
It has been, of late, and has
stained it's intended usage