The fullback has made himself unavailable for the Kangaroos in next month's Pacific Championship against the Kiwis and Tonga.
Ponga has cited his priority is winning an NRL premiership at the Knights with a full pre-season.
He now faces a potential ban for a breach of contract - players must be available for representative honours unless given an exemption.
Johns has labelled Newcastle management incompetent for mishandling the issue, and suggested fudging tactics instead.
