If you pay for admission you create a contract with the owner, and terms of admission are often used to restrict or take rights in your photos. These are often stated in small print on the ticket itself so you cannot claim you were not made aware of the terms of the contract. Motorsport and other sports venues are particularly fond of these conditions, sometimes claiming all intellectual property rights of anything you create, but they crop up at music venues and all manner of other places. They are open to legal challenge, mainly on the grounds that they are unfair and/or that the terms were not stated before payment. It's worth remembering that a copyright assignment has to be in writing. But a court would ask why you didn't immediately return the ticket and ask for a refund if the terms were unacceptable. The safest course is to boycott such venues - and report them in the forums here, so others can do likewise.