Almost all casinos have restricted regions that are not welcome and that is not because the casino does not like people from that region but to prevent jurisdiction that could extend to sanction the casino for not having a registration in their region before allowing gamblers from their to use the casino.
Marketing has been a way of informing the public about what users or customers should be expecting when they start using their products. Every company or project has product or services that is rendered to people or customers. The quality of the product or services is what will determine if people will continue using the services or not. Most of the top and well recognized casinos in the gambling industry were able to reach that level because of how customers valued their brand.
Casinos doesn't want to get a trouble from allowing those people from country that ban gambling. It is a prevention from the casino but we know that those people can still visit the casino easily. Casinos can not prevent from those people so they just see the reality after those people verify themselves.
In this matter, casinos have the right to warn to those people not to use their casinos to playing gambling. But they can not do anything if those people still want to gambling in their place. Casinos still doing promotion because that is their way to grow their business. From that promotion, they will see from where people come from.