It should be easy to document that you’ve been a longstanding member of a church, temple, etc. If that place provides records, you’re in. And it should be easy enough for our authorities to validate that it’s a real church that’s been around a while. If you’re an atheist/agnostic it might be more difficult to prove you’re not a Muslim. But if they get filtered out too, no big loss.
Every person who wants a visa/entry in to the US will need to be able to prove they’re sufficiently religiously non-Muslim? If a person from Argentina happens to be agnostic and can’t prove they’re not Muslim, too bad? If a person is marginally “Christian”, but doesn’t attend church or belongs to a church or sect that doesn’t believe in any sort of official documented church membership or is in an area where nothing like that is officially recorded in any sort of documented way, then we can exclude them without further consideration.
Our government will need to check each set of documentation to verify that their proof isn’t a forgery. Given that there’s no standard for how church attendance, baptism, church membership, etc. is recorded or documented there will be thousands of different ways this could be “proven”. We’ll need to keep track of what kind of documentation comes from where and what a valid copy looks like, of course this kind of proof may change over time, so we’ll need samples of the various forms used over at least the last half century. Maybe we’ll create a form that needs to be filled out by some official from the church and signed. Either way, we’ll need to vet every religious organization around the world once a person gives a reference from that org to verify that it isn’t a front. We’ll also need to check on each piece of church-supplied documentation, too, calling to get a verbal verification from some sort of church official. We’ll need some sort of database of names of who the official contact is and an administration to keep track of when that official contact person changes. We may need to do a background check on the church officials, too.
Since most records of baptism, church memberships, church attendance don’t have a photo we’ll also need to take pictures and send to the appropriate organization to make sure the person applying with the paperwork is actually the person in question and not an imposter. Europe’s already had big troubles with forged documents and multiple people using the same documentation to get their credentials.
OK, that’s for Christians. Now what about Buddhists? Hindus? Sihks? Do Jehovah’s Witnesses do baptisms? Church membership rolls? What about pagans? Wiccans? What sort of proof can they provide? I don’t know enough about any of those. Sounds like a new section of an administration is needed to handle each major religion. So whenever anyone wants to come to the USA, they first need to declare their religious preference so we can send their info to the correct bureau to process it for sufficient proof.
Of course this ignores a person who has joined a religious organization and then converted to Islam. A church/temple/synagogue/whatever might not know if the person wasn’t a regular attender, or perhaps moved, that the person is no longer an adherent to Christianity/Judiasm/Buddhism/Hindi/Sihkism/whatever.
All of this comes down to trying to prove a negative (person is not Muslim). Proving what a person does or does not believe is a wild guess without getting to know a person, and even then it’s not always easy.
Banning Muslims sounds good. The trouble is in the details. ID’ing Muslims, especially when they may not want to be ID’ed is not straight-forward.
In other countries, there is a great deal of casual atheism, or, lack of continuing belief in islam. I’ve heard this is becoming common in Iran. Thus, many.young people will present as nominally moslem, but who will claim (and some, rightly so) agnosticism, atheism, or a general belief in the deity that is no longer tied to acceptance of islam.
Then there are folks who come from parts of the world with large mixed populations. Non-ideological moslems live in large numbers among Hindus and other folks. A quick look into the question will promote lying, but a zealous effort to weed out the lying moslems from the real non-moslems might be difficult, or even fruitless. It is difficult to imagine a bureaucracy doing this well.
An immigration policy that excludes moslems is fairly spongy. Either it will be over-enforced, and we will keep from coming to the US folks we should take, or it will be a meaningless filter that will only screen out the poorly-inforned.
Sen. Cruz’ policy of halting immigration from specific countries known to be terrorist hotspots seems a little better defined. It is inherently easier to enforce and inherently fairer. A moratorium on immigrants from countries with a large terrorist organization presence, or large majorities who are sympathetic to political islam, might better screen out the ones that are dangerous to America.