This is not airlines but about blacklists - irrespective of the reason:
Butlin's and Pontin's accused of keeping secret 'blacklists' of Traveller families | Home News | News | The Independent
Butlin’s said: “As with all large party sizes for breaks around the festive period, our terms state that all UK-based adults in the party must appear on the electoral register… It is essential that we can be certain who our guests are. The safety and security of all those who visit a Butlin’s resort is our primary concern.”
The client states that he is on the electoral register and can prove it and is taking legal advice.