Have you known that there is an age restriction in gambling? But it is varied among the countries in the world. I have just checked in wikipedia that commonly someone can play gambling starting from the age of 15/16/18/19/20/21 years. It depends on where he lives, every country may have different regulation related to the age restriction. Below I classify some countries based on the age restriction:
It's interesting but if you look at the wikipedia article you will see for Iceland for example, the 15 years old threshold is only for lottery. For other gambling games the threshold is at 18 years old in fact.