I have a tricky situation in my local Pokémon tournament (Tier 1). Player A (junior) and Player B (senior) are paired and playing in Round 1 of the event. They discover that Player A has illegal cards for the format in the deck and call a judge. As the judges are consulting about how to rectify the situation, Player C (master) gets up from his match and starts looking through Player A's deck and pulling out cards and setting them aside. Some of the cards are illegal in the format, and some are legal, but Player C is under the impression they are all illegal cards.
When the judge directs Player C to continue playing his own match and to stop interfering, Player C says they were "just trying to help" but does comply.
What is the appropriate infraction and penalty for Player C. Should the judge deviate from policy and assign a lower infraction because there was no malicious intent from Player C?