I am an admin on a Battlefield 2 server. If someone crashes my server is there any legal action I can take and how would I start the legal process

If it was done on purpose, then yes. You could sue them and press criminal charges against them. As for starting the legal process, you must first get a lawyer. Then, in order for the case to be valid, you must know the person that crashed your server, and not just their username, you must know the user's real name as well.