James R. Clapper, Jr., a CNN national security analyst, served as director of National Intelligence from 2010 to 2017, having served previously as director of the National Geospatial-Intelligence Agency and director of the Defense Intelligence Agency. Joshua A. Geltzer served as senior director for counterterrorism and deputy legal adviser at the National Security Council from 2015 to 2017. He is now executive director and visiting professor of law at Georgetown's Institute for Constitutional Advocacy and Protection. Matthew G. Olsen served as director of the National Counterterrorism Center from 2011 to 2014. He is now an adjunct senior fellow at the Center for a New American Security and a lecturer at Harvard Law School. The opinions expressed in this commentary are their own.

(CNN) Speaking in Davos this January, President Donald Trump promised that, "when it comes to terrorism, we will do whatever is necessary to protect our nation." It's a commitment we share with the President. In fact, developing and implementing lawful and effective counterterrorism strategies and policies used to be our jobs in the intelligence community, at the White House and at the National Counterterrorism Center, respectively. That's precisely why we are opposed to Trump's travel ban, which heads to the Supreme Court this week for oral arguments.

It's unnecessary, at odds with the Constitution, and ultimately counterproductive because it makes Americans less safe rather than more.

Effective counterterrorism policies respond to real threats, which in turn means responding to real intelligence about threats. But Trump's prohibition on entry to the United States from a number of overwhelmingly Muslim-majority countries is grounded in neither real threats nor real intelligence.

We've spent countless hours tracking and disrupting real terrorist threats. Those threats are caused by particular individuals, not the 150 million people categorically barred from our country by Trump's fulfillment of his campaign promise to implement "a total and complete shutdown of Muslims entering the United States." Moreover, there certainly aren't countrywide threats emanating from the nations affected by Trump's travel ban, given that no national from any of those countries has caused any of the terrorism-related deaths in the United States since 1975.

Legitimate threats involve specific people, and that's why our country conducts rigorous and tailored vetting for specific travelers coming to the United States. It's an approach that involves vetting those travelers across the information possessed by the intelligence and law enforcement communities multiple times, in response to threats and intelligence about specific individuals seeking entry to the United States.

Read More