With all the news on the virus anyone attending a football game is aware of the risk. You can't sue a baseball organization after being hit in the face with a foul ball. You can't sue a ski resort for injuries due to a mogul that wasn't properly groomed. You can't sue a restaurant for breaking you tooth on a chicken bone when you order chicken soup. In law we call that the doctrine of "Assumption of the Risk". Now of course there are several exceptions to the rule but I can't see how any of them would apply here. One problem I do see is that if they take extreme protective measures like taking an attendees temperature and insuring the seating is compliant with social distancing, etc they are by implicating promising those attending that the arena is safe. If later its "'discovered" that not all gate keepers were instructed on how to take a temperature and (big and) if that can explain numerous virus caused illnesses that could open the door to get past assumption of the risk. Then the question becomes how valid is the signed waiver and there is an entire body of law on the validity of waivers.