Here in the US, LDS(Mormon) churches have a sign out front saying “Visitors Welcome”, perhaps in response to awareness that visitors are generally not permitted in their temples, which are separate and distinct from local church buildings. I have seen this type of sign elsewhere as well, perhaps indicating that they are afraid that outsiders will see their church as an insular community that does not want to be disturbed and is not open to outsiders.
What are some faiths that discourage nonbelievers or outsiders from attending basic services?
I have attended a conservative Mennonite service where I was the only person not in conservative Mennonite/Amish garb, but I was not made to feel unwelcome, though I actually knew one of the members socially already and thus wasn’t truly alone.
Note that I’m talking about attending services, not about converting. I know that there are several faiths that discourage people from converting to them and/or make the process very involved in order to test one’s patience, but are there any faiths that will either explicitly ban visitors from attending ordinary weekly services in general (e.g. by posting signs saying “<religion>ites only, no visitors”, placing bouncers at the door, or by calling police to have visitors arrested as trespassers), or implicitly ban or discourage them by making them feel uncomfortable?