What does a reasonable restriction make is up to the court to decide, not cops, and definitely not some federal agency.
There's a lot of precedent too, I'm sure.
So yeah, there's no real way to know ahead of time if any protest is or is not legal or legally impeded.
That's not the case with continental law where it's defined ahead of time.
I think the ACLU’s advice (which I linked to) is pretty clear about how to organize a legal protest. Sometimes the goal is to get arrested, but if you want to avoid that, then it’s not hard to do.
