Cardano gambling websites can claim to be legal in most cases, but your location dictates the answer.
There are two different aspects to consider: the legality of ADA and gambling websites in your country.
While Cardano is generally okay to use, it is a different story when it comes to gambling websites.
Still, some good ADA gambling websites accept customers even from countries where they cannot operate.
Regulators find it hard these days because many punters use VPNs to keep their online activity a secret.