Our government has legally been allowed to knock down whichever door it has wanted to for centuries assuming it has received the proper warrants. That's mostly

Our government has legally been allowed to knock down whichever door it has wanted to for centuries assuming it has received the proper warrants. That's mostly true, but not completely. There are a number of doors that have always been barred: - Self-incrimination - Incrimination of a spouse - Attorney-client relationship - Minister/priest - parishioner relationship - Doctor - patient relationship (?) The doctor simply cannot force you to bear witness against yourself. Nor can they force your attorney to reveal what you said to him. Some of these examples have a sort of exception, where a doctor or an attorney must give warning it they know that the subject person is going to commit murder, for example. But that's not the same as saying that the government can go back and look at past communications.