It can only be if the authority implements strict measures to enforce this kind of law on every registered online casino. However, people would always find a way to break this law without getting noticed, by using multiple accounts. They can use other people's identities to register on the platform. Self-exclusion will work, but it won't eradicate gambling addiction.
If both the authorities and casinos are serious about combating gambling addiction, this can make a huge difference. However, money can bend laws sometimes.