it started after the shooting in san bernardino, california. >> donald j. trump is calling for a total and complete shutdown of muslims entering the united states until our country's representatives can figure out what the hell is going on. >> trump has described his position many different ways but never withdrawn the actual muslim ban proposal, even saying he'd expand it on "meet the press." >> i actually don't think it's -- in fact, you could say it's an expansion. people were so upset when i used the word muslim. oh, you can't use the word muslim, and i'm okay with that because i'm talking territory instead of muslim. >> the new msnbc legal unit investigation provides the first comprehensive policy analysis of how a temporary muslim ban could actually be administered. chief legal correspondent ari melber is here with me. with the work collectively with the united, what were you able to break down and figure out what this would mean if it would actually go into place? >> trump has...