They won't be able to not permit people from bringing their cigarettes into the parks. Too many rely on Disney transportation and won't be able to stow them in a car.
Easy solution to that. I'm sure there will be notices and advertisement about this all over the World. If they do decide to not let any into the parks, you have been warned, and they can simple tell you it's not allowed in the parks, period. You'll then have the option to being it back to a car/hotel if able, or else into the trash. Just like airports not allowing certain items passed the security checkpoint. There is the rubbish.
Is that fair? Is that something they will actually do? Who knows. But to say they "won't be able to not permit people" isn't true at all.