Suppose you agree that there is a humanitarian crisis at the border - does that mean that the president is authorized to do anything he says is addressing the issue?
For example, "there is a national emergency at the border, therefore I am buying a new Air Force One jet (hopefully a Boeing Max8) to address the issue."
Whatever this humanitarian crisis is, I don't think a wall has much to do with it. First of all, it's not a humanitarian crisis to American Citizens, but rather only to the migrant caravans.
The wall can't help them. Obviously, it does not afford them the humanitarian aid of the United States, but rather refuses it. Even if the supposed deterrent aspect of the wall magically stopped the migrant caravans, the people that would have made the journey are now stuck in unlivable situations in their home countries. Their humanitarian crisis hasn't changed at all.