Gambling is generally a regional thing and is subject to each state. Usually it’s governed by where you are currently.
Cruise ships on the other hand are governed by the country the ship is registered in and/or by whatever country they’re docked at.
So a law will state specifically that there is no private gambling allowed within the confines of a certain geographical area such as the state of Washington, for example. The law can also make provisions that gambling is allowed on Indian reservations or within certain city limits.
The cruise ship leaves the geographical area where gambling is not allowed and allows gambling to occur in international waters which is fully law-abiding.
Also, most states and governments will provide licensing for casinos. If you qualify you may proceed with gambling in that jurisdiction.
I assume when you say stateless you are probably referring to the United States. Although there are other country’s with states but nevertheless the same would still apply.
You gotta be from somewhere. If you’re indigenous in the state of Ohio you’re still a resident of Ohio in the country of America. All laws still apply.
If you’re referring to something like a sovereign citizen all laws still apply regardless of what people like that may believe.