We all agree that the United States faces real threats from terrorist networks and must take all prudent and effective steps to combat them, including the appropriate vetting of travelers to the United States. We all are nevertheless unaware of any specific threat that would justify the travel ban established by the Executive Order issued on January 27, 2017. We view the Order as one that ultimately undermines the national security of the United States, rather than making us safer. In our professional opinion, this Order cannot be justified on national security or foreign policy grounds. It does not perform its declared task of “protecting the nation from foreign terrorist entry into the United States.” To the contrary, the Order disrupts thousands of lives, including those of refugees and visa holders all previously vetted by standing procedures that the Administration has not shown to be inadequate. It could do long-term damage to our national security and foreign policy interests, endangering U.S. troops in the field and disrupting counterterrorism and national security partnerships. It will aid ISIL’s propaganda effort and serve its recruitment message by feeding into the narrative that the United States is at war with Islam. It will hinder relationships with the very communities that law enforcement professionals need to address the threat. [my emphasis]Fred Kaplan judges that the Executive Order (EO) shows, "He doesn’t seem to understand the political nature of war or the strategic consequences of politics." (The Commander Stumbles Slate 01/29/2017)
Vladeck also explains:
The statement also assesses that “the Order will endanger intelligence sources in the field,” which is notable since the signatories include John McLaughlin and Michael Morell, who served at different points as Deputy Director and Acting Director of the CIA during the George W. Bush Administration.
The group’s statement also calls into doubt any deference that might normally be given to executive branch decision-making. “The ‘considered judgment’ of the President in the prior cases where courts have deferred was based upon administrative records showing that the President’s decision rested on cleared views from expert agencies,” their statement reads. “Here, there is little evidence that the Order underwent a thorough interagency legal and policy processes designed to address current terrorist threats [and] we know of no interagency process underway before January 20, 2017 to change current vetting procedures.” [my emphasis]
Also at Just Security, Cristina Rodríguez expands on that point (Trump and the Immigration Bureaucracy: Should We Expect Civil Servants to Dissent? 02/09/2017):
By all accounts,... it appears that the Trump White House failed to enlist the relevant agency heads, much less their knowledgeable civil service personnel, when formulating the order—bypassing inter-agency consultation that could have highlighted operational concerns. The initial chaos at the airports in the days after the order’s release, and the administration’s repeated change of position on whether the EO applied to green card holders, suggest it had no real insight or plan for how to provide implementation guidance. The airport turmoil was only exacerbated by the nature of customs and border officials’ jobs. Officers at ports of entry have considerable discretion when determining whether to allow a non-citizen into the country. They know it, and they operate with that frame of mind every day. The administration’s failure to communicate the meaning of the new order created uneven enforcement. The sweeping reach of the order further amounted to a shock to the system, opening the door to overbearing law enforcement and excessive hardships for families and others.Personal rule of the United States may be turning out to be harder than our new President expected.
Amazingly enough, the absence of inter-agency consultation and communication with the bureaucracy might actually become relevant in the litigation, as courts seem willing to question the President’s national security judgment in light of the haphazard formulation and implementation of the order. His disorganization and poor planning is an indication that national security may not have been his motive at all. [my emphasis]
But, as Dahlia Lithwick says, "There is no longer any doubt that President Trump is at war with the federal judiciary. The more the courts align against him, crossing virtually all ideological and political divisions to do so, the more he insists they are partisan and “political” and willfully endangering the country." (Why Trump Has Declared War on the Judiciary Slate 02/10/2017)