Trump may revive a program that was in place from 2001 to 2011; according to The Washington Post, that system “required people from countries deemed ‘higher risk’ to undergo interrogations and fingerprinting upon arrival” and, in some cases, “to follow a parole-like system by periodically checking in with local authorities.” Most of the countries identified as high-risk were majority-Muslim, and civil rights groups charged that the program targeted Muslims. But to call such a program a “Muslim registry” creates an essentially false impression — which is what many people were undoubtedly left with if they did not read the story carefully, or only saw the buzz about it in the social media.
Sifting through those messages to determine which, if any, need to be taken seriously is the responsibility of the Secret Service Internet Threat Desk, a group of agents tasked with identifying and assessing online threats to the president and his family. The first part of this mission—finding threats—is in many ways made easier by the Internet: all you have to do is search! Pulling up every tweet which uses the words “Obama” and “assassinate” takes mere seconds, and the Secret Service has tried to make it easier for people to draw threats to its attention by setting up its own Twitter handle, @secretservice, for users to report threatening messages to.
The decision doesn't have to be logical; it was unanimous.