The constitution applies to citizens. No one has the right to come to the United States that is not a citizen, ever. Right now, terrorism is a big problems. Nobody wants themselves or their loved one to suffer at the hands of terrorism. There is nothing wrong with pausing the process until we can make it safe.
Trump's travel ban has many flaws.It caused chaos everywhere. It also missed out on countries that many terrorists come from or sympathies with.Many terrorists come from the Middle East.Gulf states often sponsor terrorist activities and Mosques that support Terrorism. If Trump wants to crackdown on Terrorists, he should focus more on the Gulf states.
The immigration and travel ban that Donald Trump has put in place is a disgrace to this country and is setting us back more than fifty years to a time where intolerance ran rampant. This ban is not a solution to any problem, all it is doing is worsening the opinion that the world has of the United States. This was a nation founded on immigration and we have a big statue that welcomes all immigrants to a life of liberty and the pursuit of happiness. This will more than likely NOT stop terrorism because the ones that are going to commit these acts will find a way in and the only people Trump is stopping from coming in are hardworking and honest people just trying to make a life for themselves.
The travel ban is something new and right now it appears there are many questions. While a suspect may be from a specific country, it does not necessarily mean they are a citizen from that country or living there as a temporary visitor. Therefore, more research would have to be done before making any decisions on what the travel ban will actually involve.