It is filled with limits on what he can and cannot do. By Signing it is he not agreeing to those limits? The Rat Judges have shown they will ignore it when he is on solid ground let alone when he tries to get around something he has already agree to.
When the case against the wall gets to the Supreme court, I do not think it is going to be as easy the media thinks. Article 4 gives quite a bit of responsibility to the President on border security. I would like to see responsible analysis of this.