That means the Packers can’t sell single-game tickets to them. It also means the Packers must end the practice of allowing people with disabilities who hold season tickets to sell unwanted tickets back to the team. Under the new rule, they’ll have to sell them to family, friends or strangers, or absorb the cost of an unused ticket, the same as everyone else.
I'm not sure the Green Bay Packers have gotten this legal interpretation correct. Here's the Americans with Disabilities Act (ADA) law in question, which says in the overview:
Direct purchase options have simply been unavailable to many individuals with disabilities because transactions frequently could not be completed. Instead the purchaser was directed to send and e-mail or to call a separate telephone number to request tickets and wait for a response. The burdensome policies still exist, making it difficult or impossible for those who require accessible seats to purchase tickets, especially for popular events that sell out in minutes.
So all ticket sales have to be made in the same way. If every Packer fan buys a season tickets, then those who need to purchase an ADA accessible seat must be a season ticket holder too? Is it illegal for the Packers to sell single game tickets? Maybe that's how it seems on a literal reading of the law, but the intent as stated in the overview isn't to force everyone who needs an accessible seat to become a season ticket holder.
If the law is intended to give people with disabilities more access to public events, and the result is to effectively take that access away from Derek Vreeke, then it doesn't seem like the law is working or being applied correctly. The Packers aren't intending to do the wrong thing here, and it seems like they need to follow up with the agency who enforces the law to get a better result.