Prime Minister Netanyahu has signed an order to revoke and expel two Israeli Arab Muslim citizens convicted of terrorism. For any democracy to survive, citizenship cannot coexist with active allegiance to those who seek its destruction, and Israel has finally taken a first step in that direction. It is small, late, and insufficient on its own, but it signals the beginning of a necessary process. Other Western democracies facing similar internal threats will ultimately have to confront the same reality if they intend to preserve their sovereignty and security. There is no other way.