The heating element couldn't be electric. For sous vide, if you can maintain that temp in a smoker for a long period of time he'd be good to go from what I know of the rules. I don't believe that there is a rule against putting your meat in a bag, vacuuming it and dropping it into circulating water around 140 for a long time. Technically, it's so far removed from bbq. I think since it's cooked submerged underwater in a bag that all of us know how the ruling would come down on this one.
Ah here we go. I looked at the rules KCBS 2011:
8. Parboiling and/or deep‐frying competition meat is not
I really think that rule, while a lawyer may argue it, would cover sous vide.