Someone pointed out that the government doesn't need anyone's cooperation to create a registry of Muslim Americans; they can do it based on available data.
Note that a reputedly leaked document says that Trump ordered the government "collect and make publicly available within 180 days ... information regarding the number of foreign-born individuals in the United States who have been radicalized after entry into the United States and engaged in terrorism-related acts". [0] They could make many lists without anyone's cooperation.
Note that a reputedly leaked document says that Trump ordered the government "collect and make publicly available within 180 days ... information regarding the number of foreign-born individuals in the United States who have been radicalized after entry into the United States and engaged in terrorism-related acts". [0] They could make many lists without anyone's cooperation.
[0] http://www.huffingtonpost.com/entry/read-draft-text-trump-ex... - I don't usually rely on the Huffington Post, but as an example of the possibilities the accuracy doesn't matter as much.