My vote would be that its legal if your battery pack and or ESC is next to your CO2 valve. Heaters tend to be electric blanket type gizmos that you run when the rest of the bot is powered down (like the tire blankets used in F1) which an ESC is not. There is also no rule to say we cant used liquid cooled electronics (such as you find in gaming PC's) so who's to say if the CO2 is cooling the ESC or the ESC is heating the CO2?