Trumps claims that he can invoke Emergency Powers to build the wall is NOT a bluff....and the left KNOWS this. That is why they are screaming so loudly that he CANNOT do so in the effort to fool the populace into thinking he can't.
However thanks to Dubya the Shrub who signed The Patriot Act and Obozo the SCOAMF doing the bidding of his puppet master Jarrett ( and with the happy and willing compliance of Congress) created dozens of new rules and orders to expand Executive Power we now have a situation where the President can, if he chooses do pretty much ANYTHING he want to. Of course when the "deep state" was creating this situation they truly believed they would ALWAYS own and control whoever controlled the White House. They did not believe anyone like Trump would come along and take the office and not bow down to them. So yes....Trump CAN build the wall via the plenipotentiary power he has thanks to the conniving and plotting of the bureacracy.