I'm asking for a clarification from Ms. Chow.
I'm not sure that adding the word “heretofore” beside “substantive” actually gets to what you're trying to do.
I believe it should be “with subsection (4) is prohibited heretofore from providing substantive immigration advice”. If it's “prohibited heretofore”, it means “prohibited from this moment forward” from providing substantive advice, which I believe should be the logical grammatical reading of the intent.