With coinbase they track which wallets receive a lot of traffic and amounts of those transactions. If a wallet receives too many high BTC deposits they flag it as an illegal entity. They don't need any proof n can cancel the sources account n ur account without warning. Once they close ur account n force u to transfer the remaining BTC to another wallet. U don't loose whatever money is left in ur wallet.
However ur source should be smart enough to be using a new wallet for each transaction. Prevents this from happening. I've been sending everything straight from coinbase with no issues for the past 6-7 months. Fuck paying those extra fees.