if your bitcoin was lose and already being moved to another address that's not belong to you, so you can't do anything unless you know who's the one that steal your bitcoin there's still a chance,but if you didn't it's mean you're losing,the most better option is to prevent from losing by enabling any security option to the highest security
1. even if you know the person who had stolen your coins, you cannot do anything unless the hacker wishes to return the btc back to you.
2. bitcoin is not backed by any law and government so it would to useless to think about filing a case against the hacker.
3. btw, just for your extra information, there is a possibility to revert a btc transaction by double spending only if the main transaction is unconfirmed.
4. with bitcoin, "you are your own bank" and you have to take care of your own bits. so we say that never store your bits in an online wallet because they are the least secured wallets.