However, without some statury guidance, it’s hard to show (absent a Rod Blagojevich type tape) that the exericsie if discretion falls outside actual legal discretion

I think it’s unlikely the Supremes would buy this argument. They’re more likely to say that what Congress meant was that when the issue comes up in a suit, we expect the AG to look at the facts of whether X, Y, and Z happened, and if they did — it’s a simple factual finding, not a legal analysis — to so certify. That plausible reading makes sense of the statute and preserves Constitutionality (and is thus preferred).

And since the prior AG has already made the certification, the point is moot.

What is the counter-argument to this?

It’s pretty clear that the public and the media aren’t on the same page. An earlier Washington Post poll showed basically the same thing.

Poll: Most want inquiry into anti-terror tactics

snip.

Close to two-thirds of those surveyed said there should be investigations into allegations that the Bush team used torture to interrogate terrorism suspects and its program of wiretapping U.S. citizens without getting warrants. Almost four in 10 favor criminal investigations and about a quarter want investigations without criminal charges. One-third said they want nothing to be done.