So you want to play at an online casino and you are not sure if it is legal where you are? This is one of those difficult questions, because each country has its own laws regarding land and online based casinos. When you sign up to a casino, they will be able to tell where you are from and if you are in an area where it is not allowed, then they accept any responsibly over the legal issues.
Online casinos are often located outside a host country, so that they avoid the laws that the particular country imposes. This allows players to play there legally. A law in the USA stops US banks processing card transactions to casinos, but the simple go-around for this is to use an intermediate online payment site. The ones accepted are usually listed on the casino you want to play at.
Laws are imposed by countries to stop what they consider “harmful effects” of gambling to their citizens. Some countries such as Russia prohibit online gambling altogether. Others have specific rules that protect certain things. Generally if you have any doubts you should contact your local authorities.