But I am very sure most of such cases are not related to government asking custodial services to lock it, I believe the custodial companies will in this case have the coins with them, a way they are the one stealing from others. Or is it not stealing? Some peoples accounts are locked and they are not scammers and also not involved in criminal activities. I have seen cases the victim will send them messages but nothing will still be done.
It's difficult to determine in some cases, if it's in the scenario of a scam exchange, more often than not, they are new exchanges, and they lock users accounts immediately they deposit into it, then such act is clearly stealing; that's why users aren't expected to deposit funds into every new exchange they meet, and even if they must, then a tiny amount would do, so if the exchange turns fraudulent, the loss will be minimal.
Having said that, in cases of 'bigger' exchanges locking users accounts for one reason or another, it's somewhat subjective to them, and then remember that 'if it's not your keys, it's not your coins', they are centralized services and have a high level of arbitrary power, but I don't think it's possible they'll just outrightly steal users funds, they most times lock the account due to suspicious activity and then request further verification (funds will be lost if it's not provided) or lock the account based on government orders and wait further instructions (funds will be lost if user is found guilty of whatever), etc, it can't just basically be called stealing, but funds are being lost, the more reason there's 'a rule of thumb' forewarning users not to store funds in centralized exchanges cause in the end to a very large extent they do have the final say.