If told to do so, they will do it. You seem to place high importance below on health department protocols, so it wouldn't surprise me to see LEOs doing it for that very reason.
And here you go with this "it isn't illegal" nonsense. Is it ethical? Is it just? For people going to church services? Really?
Does the Health department have enforcement powers? I don't know, I'm asking. If so, that should be concerning to most people just as much as anything else. Or, do they rely on the police to be the enforcement arm?