I never played anywhere that allowed fakes but most players were ok with you taking a otherwise worthless card (hello Lapras my old friend) and marking the face to count as something else in Pokemon or otherwise.
Actual fakes were problematic as you can tell the back of the card apart generally.
What we used to do when I was a kid (before online stores were common to use, and had ~4 hours to the closest store selling magic cards so only got a new pack once a fortnight) was to use plastic sleeves for the whole deck. Then you can't really ser from the back if it's a printout or a real card.
you're going to sleeve it anyways, unsleeved card backs are too easy to mark. I've never played against or with an unsleeved deck in a magic tournament, even a draft.
Actual fakes were problematic as you can tell the back of the card apart generally.