There seems to be a lot of confusion in this area and i am constantly asked about Sealed DVDs.
You will find that the major Distributors such as: Universal, Paramount, Fox etc most of their movies do come sealed (shrink wrapped)
However even DVDs that i have ordered from the Distributors have not always come in Shrink Wrapped, particularly if they are on special or clearing out excess stock. One of our main suppliers for our budget area only a small percentage come in sealed.
So, the theory that because it isn't sealed, its pirated is a big call to make. A lot of distributors repackage with their branding to resell as their own (with permission) and don't shrink wrap.
The key is to ask the question of the seller if you really have any doubts. If you do suspect that the DVD is pirated question the seller but make sure you have reasonable doubt - not simply because the DVD is not sealed.
The major key to knowing pirated DVDs is the pricing and if it is sold in Australia. Each Country normally has their own release times for DVDs, you will tend to find that Australian movies are released to DVD first here and then other countries and vice versa for overseas releases. So, if a movie is still playing at our cinemas and you see it advertised here in Region 4, I would definitely be questioning the seller.
Also if a price of a new release is too good to be true, it normally is!! Distributors/Wholesalers etc normally have DVDs for a certain price. I am not talking about budget releases but the latest release - things like Chicken Little, Walk the Line etc. If it is coming from overseas, also be aware as most of the movie houses/distributors/wholesalers etc are usually situated in Sydney or Brisbane.
I hope you have found this guide helpful.