I would generally use "applicable", Mimi, and I would mean that there is some valid reason that the rule would not be apply. This would be interchangeable with saying "that rule does not apply in this case".
You could say "that rule is not applied in this case" but it might carry a slightly different implication, i.e. that someone choses not to apply it. Then again, it might not. Not too clear, I guess, but if you stick with "applicable" you'll be safe.
I think that applied and applicable are not interchangeable and the sentences that will be formed have different meanings.
1. That rule is not applied in this case. For whatever reason, this time (in this case) we did not apply that rule. Maybe there should have been a late fee for returning a book late to the library, but the librarian winked, took the book back, didn't charge the fee, and said line 1.
2. That rule is not applicable in this case. The run cannot be applied in this case. Maybe your going to a club, and they have a rule that on Wednesday, ladies get in free. If it is not Wednesday when you go, the rule doesn't apply - and you get no discount. The men pay full price all the time, because in the case of men we can say, line #2.