There is no way to stop those gamblers who don't have the control to manage their funds properly. ralle14 have already given you an answer but it can only be used in auto bet. Manual betting is fully depends on the bettor and there is no way to set max bet limit in manual betting. But you can disable max bet option, it will help a bit to those kind of gambler. Beside that you can make the best use of vault feature. Keep the max amount in your account what you would like to have as max bet loss limit. And move the other funds into vault.
I have to say I have met with people who was so much in trouble that they decided to quit, so they mailed the casinos to block them, and some casinos have that so they blocked those players so that they would never gamble there again, to help them fight with addiction. However those same people in return started to use VPN to go back in after some time, because they are literally addicted, and face problems when it's found out that they are gambling again.
So, it should basically be some sort of warning sign for many people, but there is no way to stop them for sure, they will always find a way, if they can't do anything they will just leave for another website. There is really nothing that could be solved by big enough addiction. So, limiting the amount they could gamble would not be solution, they would just remove it when the time comes.