Whoa! 900 000$ is a very huge amount of money, it's not a joke actually. There are many questions that come to my mind when I read that, actually. First, why did they put
such a large amount in coinbase?
This is a small amount of money compared to large customers that Coinbase has, and even more compared to institutions. If some amount of money is big for you and me, that does not mean that the amount of money is big. There are people who have tens or even hundreds of millions on Coinbase and they have no problem. The issue is not with the amount of money, the issue is about its suspected origins and the shady person that is behind this transaction. People who are rich or people who have very clean sources of funds and good documents do not have problems depositing even larger amounts and they accounts do not get frozen. For many transactions they are not even asked for source of funds based on their profile and history with the exchange.
I believe that in regulated casinos, you can ask for all betting data. At least EU citizens have law on their side and casinos are required to give all the data they have about the user activity if they choose to request it. That can take couple of months, but resolving these issues take time anyway.
Yes, they can contact the casino through their support and request for their deposit and withdrawal histories , including the betting histories if needed[regulated or not, doesn’t really matter for that]
The only problem is they as a gambler could be breaking some rules in their jurisdiction or country by admitting they gambled and made such money on an offshore Casino, especially if there’re tax or gambling restrictions involved [illegal gambling]. which can also lead to legal or tax problems in some jurisdictions .
“Not your keys not your coin”..
This will not help them. We have established here that it is very likely the user broke the terms and conditions and possibly even used a fake ID, they have committed several crimes to get this money. The money is fraudulent and Coinbase will not accept it. It would surprise me if they unfreeze it to send it back to him and close his account. The situation is high profile because of the many crimes that are committed and high possibility of money laundering, so it is possible that he will not get any of this money back.