If card decks were to go out then casinos probably couldn't keep making decks and they'd have to stop using them eventually so I would probably see if they'd give me a bunch of their old ones since they wouldn't be using them anymore because they've already been opened. That or I'd buy card stock and try to make some of my own. If neither of these worked then I'd probably just draw crappy cards on cardboard or on old business cards or something. Actually I've got another great idea, but it's something I already do and it pertains particularly to my character and I kind of don't want anyone copying me so I'm not going to say it at least not yet. I just know I'd probably be fine as a card magician without playing cards. Maybe a better question would be is, what if you couldn't use playing cards anymore due to some random legality or something?