Ironically, citizens of Monaco are actually not allowed to gamble and even visit Casino de Monte Carlo. They are prohibited because the Princely family did not want their citizens to gamble away their money. Sounds pretty reasonable if you ask me. Monaco is known to be strict with maintaining their status quo.
Satus quo?
The laws are from 1850, even before the casino was built, their citizens had no money then, they had nothing, it was tourism and gambling that made them rich, not the other way around, this is not like some wealthy city that is already rich trying to protect their citizens, Monaco started from scratch with this, they banned gambling for their people even before gambling was a hit in the region.
The bigger question that bang my mind is, what is the need for establishing such a big casino in such a land that gambling is not allowed by the government, and how did the casino get it license to operate in such a country for in the first place.
That was their plan even before building the casino, Monaco had no casinos and no gambling activities two century ago, they decided the only way to get rich as a small protectorate that was thrown between two major powers was to become a different place, so they started building casinos and hotels but they decided they will fleece only foreigners!