Upvote:1
The Magisterium is not exactly concerned with what you do in your time. If you hang out at the Church of Satan and listen to the preaching, that's just fine with the Magisterium. The question is, do you accept particular tenets that are at odds with Catholic doctrine? So, for instance, going to a Protestant-led bible study is perfectly okay with the Magisterium, as long as you remember and stick to the Catholic position.
Let me give a slightly awkward comparison: going to medical school means you've committed yourself to evidence-based medicine, right? The teaching authority of med school means only certain people are allowed to teach, and they're people who subscribe to those standards of EBM. So you must, in how you act etc., adhere to it. However, you aren't 'banned' or otherwise forbidden from visiting a local faith healer and listen to him about crystals, or something similar (I don't know, I've never been to one of those). The point is that the Magisterium is a quick and easy way to determine who has teaching authority you have to listen to, but it does not determine whom you may listen to.
I am no historian, so I will leave the question of whether there has been Catholic opposition to Bible study open. However, 1) the Catholic Encyclopedia is a bit dated (notably, it's pre-Vatican II), 2) it's not a doctrinal text, 3) the doctrine of the Magisterium primarily concerns who may teach from a Catholic pulpit. So clearly a Catholic school would be opposed to somebody rocking up and teaching not about Protestantism but teaching Protestantism as a doctrine. However, there is nothing wrong with examining other faiths or denominations. The understanding of Canon Law I got says that the Magisterium is primarily concerned with who may speak, not whom one may listen to.