I usually achieve success with "do not open this course" instructions by offering to bite the head off the offender.
No, actually, just telling people to not do something is usually sufficient, depending on how many people are involved and the level of trust. But, if you've got people making courses, you pretty much must trust them a lot.
I can envision a process of removing the course creator from the course and putting the course in a category where the course creator is not while the admin reviews, but that then requires a reverse process if the creator has missed something the admin can't supply.
I advocate for a virtual wooden ruler waving above the knuckles and a stern "Don't do that" as more efficient.