According to an AP article by William McCall, lawyers who will be taking an archbishop's deposition want assurances that he will not be lying under oath. The (religious?) doctrine of "mental reservation" apparently lets you get away with that kind of thing.
Which explains the wording adverted to here, in the oath in which a (for example, attorney) swears that "without mental reservation or purpose of evasion" they'll uphold the Constitution.
And here I figured it was just a nifty phrase. Turns out, it's a term of art. I'm not totally clear as to how asking someone to swear that they're swearing without lying (or holding back the truth in order to serve a higher good, or pick your euphemism) is more effective, but it certainly has a rolling majesty to it.
One could file this story under "different standards of compliance with law for the religious?" - or just cross-reference it with "Archdiocese" and "bankruptcy."
*Not all comments welcome. Flippant, facetious, fierce, or fatuous, fine. Fraudulent, felonious, fabricated, facially insufficient, and farkin' futile, fuggeddaboutit.