Terrorism by remote control: Is there any protection?

Should President Trump's travel ban on refugees and visitors from seven mostly Muslim countries be re-instated? The 9th Circuit Court of Appeals to hear arguments today. The President's massively disruptive travel ban is aimed at refugees and travelers from seven mostly Muslim countries, but nearly all terrorist acts in the US since 911 have been committed by US citizens. Furthermore, there's new evidence that ISIS recruiters and handlers operate remotely — without anybody having to cross any borders at all. Rather than focusing on keeping potential terrorists out of the country, should we focus on those who are already here?