It is true that every state of US has its own different legal age to gambling. In New Jersey, 21 can be considered as the minimum age to play and accept the gambling service. Meanwhile, you can even play the gambling service at the age of 18 when you live in Delaware. You just need to match the rule with your current location so you know the truth. However, age is not only the main reason for casino sites to ban people from playing. If you play the gambling games outside the borders or the state, you will be on the Blacklist and you will be banned to play.
It means, you need to be exactly stay in the state with legal casino to play. You and also your body must stay in the state to play and access the casino service online. If you go outside the state but you access it, you will get into trouble and you will be prohibited to play. Physically, you need to be in the same state as the online casino offers the service. However, it is not all because online casino has another way to ban you from gambling even from the beginning related to your background.