Possession of cards

[Malachiracer]

Do you have to own all cards that are in your deck under tournament rules?

[BlackJester]

Do you mean can you borrow some cards from a friend?  Yes. As long as you use those cards as registered at the beginning you should be fine. I don't think you and a friend could, say both use the same {Elsh Norn, Grand Cenobite} in each of your decks.