First sale doctrine applies, they don't have any right to tell you what you can do with items that you've purchased but I've already said that. If they have a problem with what they believe to be people capitalizing on the discount, take away the discount or limit the number of items purchased. They have the ability to see what you are purchasing, which means they already have the ability to constrain it.
They don't have the same access they did before, as it has been taken away. Yes they can buy a ticket, but why should they when Disney may be breaking the law by restricting their ability to access the parks for doing something that is within their legal rights?