Of course, the president is never going to order anything but the arrest. He'll just comment that it would be too bad if the arrestee resisted. Wink, wink, nudge, nudge.

If that actually worked, then he wouldn't be able to be convicted of a crime even if he didn't have immunity. The judge would dismiss the case. Right? I mean, the idea is that a judge would be so naive or stupid or corrupt that he would accept the above state of affairs as absolving the President of complicity in the killing for the purpose of making the official acts determination - so that judge would make the same call on the motion to dismiss the charges.

What about this sentence from the USSC decision? Page 7, first full paragraph, last sentence:

Testimony or private records of the President or his advisers probing such conduct may not be admitted as evidence at trial.

Sure sounds like testimony from his advisors - including anyone he talked to about the arrest - is protected information and could not be used.

Nope. It doesn't say the evidence can't be used. It says it can't be admitted as evidence at trial.

It's not privileged - that was shot down in U.S. v. Nixon. It's inarguable that it can be used in the criminal prosecution of everyone else involved in the murder conspiracy (none of whom have immunity), which means that it can be obtained by investigators. And nothing in the opinion says it can't be used in the judge's determination of whether or not the underlying acts are immune acts or not. In fact, the opinion specifically allows the government to rebut the presumption that the actions are not within the scope of immunity, which requires that the government be allowed to use the evidence to make that showing. The evidence can't be used at trial to support other charges, because that would erode the protections of immunity - but allowing it to be used to determine whether an action is or is not entitled to immunity doesn't implicate that concern.