This all depends on the laws that govern the jurisdiction you live in. It is your responsibility to make sure that you have the legal rights to play the games at the casino. The casino itself cannot determine the state of the law in every jurisdiction around the world at all times. So, it is your job to determine the legality of use in your jurisdiction.
When you open an account the casino requires that you agree to the Terms and Conditions of Use before you even create your account. This means that you are of legal age to gamble, so you need to be at least 18 or 21 to be legal to gamble, and that depends on the area you live in. The casino doesn’t accept anyone who is under the age of 18 to open an account and play for real money.