Vapor barriers are sort of an oxymoron in how they work. The idea is to keep exterior moisture/vapor from coming into the living space , but if there is any moisture present, it will trap it in the wall studs and insulation if there is a vapor barrier over the studs. This is where all of the bad mold and mildew comes from. So, if your basement is not sealed from the outside, putting plastic on top of studs and fiberglass is really not a good thing to do -- Even if required by code.
A better remedy is to coat the interior cement/block with a water-tight coating. I use a 2 part polyimide epoxy on concrete for this and many other coating work my company does. It's cheap and not hard to do, but it is very messy and very smelly. In fact it is deadly if used in a confined space without proper safeguards, clothing, and breathing equipment. So, not something I would ever recommend a home owner/handyman do, but it is the best answer for existing basement vapor protection.
I am currently doing my own HT. One of the very first things I did was coat all the floor and walls this way. I had a dry basement, so there wasn't any need to any water abatement/mitigation, just the coating system itself. With a properly waterproofed basement, there isn't any need for any vapor barrier, except in showers/sauna's/baths and such.