At 4:00 is a choke I've pulled off in class, but i suspect is illegal. I'm having trouble, though, finding rules that state such. So, is it legal, and if not what are the rules that state such(link please if there is one)?
I presume you mean under Judo rules. (From your use of “Shido”.) (It’s totally legal in BJJ. )
Why do you think it might be illegal under Judo rules? Because you’re choking the opponent with your own gi rather than with theirs? I’ve never encountered such a rule, although I’m not expert in all the minutiae of the current rules. I think you might get a penalty for the variation at 4:11 where he held his gi in his teeth for a moment before passing it to his other hand. I don’t think that’s allowed.