Trump's immigration ban violates core American principles and is patently unconstitutional. It turns away refugees fleeing unimaginable violence, when refugees already are subjected to the most extreme vetting any immigrant undergoes, from months of interviews to redundant background and security checks by law enforcement and intelligence agencies and the state department. Plus, only the most desperate cases are put forward for resettlement in the first place. The United States takes in only a tiny thimble-full of the refugees who need resettlement, but we take them in to uphold international standards of conduct we have long fought to keep in place. If we send the message that it's okay to close the door to refugees, and to single out Muslims for exclusion, we will fuel the very extremism and instability this ill-considered order is supposed to protect us from. This order needlessly turns away refugees who desperately need our help, and imposes an unconstitutional religious test on would-be immigrants. It should be noted that no citizen of any of the seven Muslim majority nations listed has ever taken a single American life. This order cannot be justified on the basis of security and would only help our enemies to recruit new converts. For the sake of our principles as well as our security, Congress must act to overturn this un-American, unconstitutional order at once.