"banned" is not the right word.
Pokemon TCG has a couple of different formats.
All cards except Ancient Mew all allowed for Unlimited Format. (Ancient Mew would be the only card currently "banned")
Some local tournaments are in this format and many leagues allow play in this format.
However, all Premeire Events (those that Pokemon Organized Play support with prizes and that earn points toward an invite to Worlds) are in the Modified Format.
Modified Format has a list of sets that cards can be from (as well as older copies of cards that have been reprinted in those legal sets).
That list is the sets from the last couple of years and every new set as it is released. A few sets rotate out every year after the tournament season ends, after Worlds.
Currently, Holon Phantoms and up are legal for Modified.
Want to see all the legal sets and the cards in those sets?
Check out our Researching Tower:
http://pokegym.net/tower/
They are all there.