This executive order revised the President's previous Middle Eastern refugee and travel moratorium. It removed any mention of religion, decreased the percentage of the world's Muslim population affected by the ban, and laid out a synopsis of why conditions in Syria, Iran, Yemen, Libya, Sudan, and Somalia made vetting currently impossible.
The Executive Order explains that Syria is in the midst of a civil war, Libya and Yemen are active combat zones, Somalia is a failed state with terrorist safe havens, and Sudan and Iran are designated State-Sponsors of Terrorism. For these reasons, the President has determined that full vetting is simply not possible.
This summary justifies President Trump's use of the powers granted to him by 18 USC 1182 (f):
Whenever the President finds that the entry of any aliens or of any class of aliens into the United States would be detrimental to the interests of the United States, he may by proclamation, and for such period as he shall deem necessary, suspend the entry of all aliens or any class of aliens as immigrants or nonimmigrants, or impose on the entry of aliens any restrictions he may deem to be appropriate.
Judge Watson, however, sees the executive order differently. Even though it makes no mention of religion whatsoever, he has determined that it likely constitutes a de facto "Muslim ban." Here is how the Judge justified his decision:
"It is undisputed, using the primary source upon which the Government itself relies, that these six countries have overwhelmingly Muslim populations that range from 90.7% to 99.8%. It would therefore be no paradigmatic leap to conclude that targeting these countries likewise targets Islam.”
This one paragraph, if upheld and allowed to stand, will send the United States into a Constitutional crisis.
For something to be discriminatory, it must target an individual or group of individuals because of their protected identity. This is true in both US and International Law.
As an example, for a US crime to be classified as a hate crime, it must be perpetrated against someone because of their ethnicity, race, gender, religion, or disability. It is not enough for the victim to simply belong to a minority group. They must have been targeted because of their identity in order for a crime to be classified as a hate crime
The same logic appears in International Law to classify certain crimes against humanity. Genocide, for instance, is the "attempt to destroy, in whole or in part, a national, ethnical, racial, or religious group." If the President orders an airstrike and it kills many people in an ethnically homogenous village, that isn't enough to qualify as genocide. Individuals would need to be targeted because of their identity.
Executive Order 13780 doesn't pass the "because" test. Sure, telling Iranians they are are prohibited from entering the United States for 90-days undoubtedly negatively affects Muslims. After all, the country is officially 99.7% Muslim. But the fact that that non-Muslim 0.3% of the population would also be prohibited from entering the United States proves that the Executive Order does not target individuals because of their religious beliefs.
This is what makes Judge Derrick Watson's ruling so concerning. He has determined that President Trump's refugee moratorium is unconstitutional because the countries affected by the order have populations that are 90+% Muslim. He concludes that "targeting these countries likewise targets Islam."
So let's flesh this logic out a bit.
The Bush Administration went out of its way to make sure the Arab world understood that we were at war with terrorism, not with Islam itself. But according to Judge Watson's logic, because Iraq and Afghanistan have 99+% Muslim populations, "targeting these countries likewise targets Islam."
The Islamic State of Iraq and Syria, as the name suggests, is a terrorist group made up entirely of Muslims. Recently, President Trump ordered US Marines into Syria to take the fight to ISIS. For the last few years, the US Military has bombarded ISIS positions by air and by sea and Special Forces have helped coordinate operations on the ground.
If Judge Watson concludes that a national security decision targeting foreigners with no connection to the US is unconstitutional if the majority of those affected are Muslim, how can the United States possibly wage war against the Islamic State?
This is the slippery slope. When a District Judge in Hawaii can halt a national security directive simply because it would affect individuals who happen to share a religion, then the Executive Branch loses all power to conduct foreign policy.
Judge Derrick Watson pointed to President Trump's campaign rhetoric that was highly critical of Muslim immigration as one reason to block the travel ban from going into effect.
Depending on which statistics you use, somewhere between 52-54 countries out of the total 196 countries on earth have Muslim-majority populations.
Does the President of the United States now lose the ability to conduct foreign policy related to more than 1/4 of all countries on earth simply because of comments he made about Muslims on the campaign trail?
Conversely, does US aid to Israel, the world's only Jewish-majority country, become unconstitutional because it favors one religion over others? Does the President lose the ability to implement policy related to the Holy See because Vatican City's population is 100% Christian?
These questions, while foolish yesterday, are suddenly legitimate. You can see the slippery slope if all of a sudden foreign policy actions for/against a country are equivalent to actions for/against that country's majority religion.
In case you're looking for a silver lining, if President Trump is only allowed to enact foreign policy pertaining to the countries on earth with majority-atheist populations - of which there are none - then perhaps the administration's call for significant budget cuts at the State Department is justified after all...