Of course they do - they modified their contract of carriage - which you basically agree to why buy a flight (https://www.united.com/en/us/fly/contract-of-carriage.html) it’s the same mechanism they use to deny you boarding if you are barefoot etc.
Sorry friend, I sarcastically was saying united cannot enforce their rules in cafes et. al.
Sorry friend, I sarcastically was saying united cannot enforce their rules in cafes et. al.