CCing your boss on everything will not save your ass (it can help, but only if your boss has not made up his/her mind already).
Your solution is technically possible, but is not a guarantee to work, as he doesn't have all the log in information for the domain registrar, and/or the registrar likely could give (<) a shit.
Anyway, I am in the lawyer camp. I was in a totally different aside from employment related issue (I was looking to sue my employer for hostile environment) I was able to meet with a competent lawyer for about 30 min, lay out my case, and get sound advice, totally free... Advice that cost the lawyer money to give me:
Don't sue. If you do you will win (and I'll take it on contingency), but you will also need to find a new line of work. If you love what you do then file a formal complaint with HR and let it die on the vine in the office, because once this goes to court your name will be known as a litigant in your industry and no one is required to give you a job.
My point to tomhudson being that not all lawyers are self serving greedy assholes (though the ones that are give everyone else the bad name).
Now in the OP situation he is trying to mount a defense of his good name, I would expect that a lawyer would charge you, but I would find one that would charge a reasonable amount, and would be capable of mounting a counter suit for slander/libel/unfair dismissal should things go sideways.