On the grounds that it WASN'T legal when the infractions occurred. Hence his show cause.
Two separate discussions. One is the show cause. The other is Pruitt's threat to name boosters who paid players.
You're right about the NCAA imposing the show cause. In today's world, I'm not at all sure the NCAA has the power to enforce that. So it strikes me as a definite avenue for Pruitt to pursue.
But, that wasn't the issue that started the thread. What started the thread, and what I was referring to, is that Pruitt was threatening to name boosters who paid players. In response, there was speculation as to what that might mean for either the boosters as individuals or UTe as an institution.
My point is that it doesn't matter if he names them and posts video and bank records online. What they did was against NCAA rules around eligibility at the time. But the NCAA has said it will no longer pursue pay-for-play violations that occurred pre-O'Bannon.
IOW, even if Pruitt names names and has hard proof, it means nothing as far as any punishment for UTe or the boosters. Salacious, maybe. But nothing will come of it.
In any case, as another poster correctly pointed out, Pruitt himself wasn't nailed for presiding over boosters paying players. He was nailed because he, his wife, and his staff paid the players directly. That's what led to the show cause. And to the extent that it matters anymore, it's still against NCAA rules around eligibility.