The problem with cats is that disciplining them typically serves no real purpose. If you swat the cat with newspaper when it gets on the gecko enclosure, the cat won't learn to stay off the enclosure, the cat will simply learn to stay off the enclosure when you're looking. What you need to do is to make the ENCLOSURE something unpleasant for the cat. This has worked for me with our cats, so maybe it will work for you as well.

Buy a roll of the 1.5" or 2" wide packing tape. Cheap is fine for this purpose. Cut strips of the tape and lay it STICKY SIDE UP on top of the enclosure, and if necessary, hanging sticky side out down the side. The cat will get the tape stuck to its paws and fur each time it tries to get into or onto the enclosure, and if you keep replacing the tape, will soon learn that being around the enclosure leads to something unpleasant for it.

I've used this method to train our cats to stay off the top of our anole tank, my BP enclosure, and the entertainment center. It might sound a bit mean, but not nearly as mean as possibly having your cat eat your gecko(s).