User blog comment:B214/Volume 22 spoilers/@comment-182.53.88.122-20160724082440/@comment-24.113.252.213-20160724160413

I think the Triaina and CCP are only cheat moves if Issei uses them while he's fighting as a Pawn. Since Pawns are only supposed to promote when they enter enemy territory, Issei would have to go by the same rules. The only reason he was allowed to use these abilities however he wanted in the Rias vs Sairaorg RG, is because Sairaorg wanted there to be no rules or limitations in their game like there were during the Rias vs Sona RG.

So, since Issei is now fighting as a King, he isn't limited by the same rules as a Pawn. So he should be allowed to use all of his abilities as he desired, unless there are any rules and limitations put on him and his team like in the Rias vs Sona RG.