Sullivan is not arguing dropping the charges, Sullivan is arguing that Flynn committed perjury when he gave his plea. As bizarre as it seems, Sullivan et al are saying...Flynn committed perjury in the court because he falsely said he was guilty.IANAL, just a humble student of the English language. As such, I would say that the "how" in "how do you plead" refers to a manner, an approach; whereas any statement or testimony offered as truth to the court would be "what" one pleads, and that isn't the question they ask. It's a formality.
But even that aside, if Flynn's plea is perjury, all plea bargaining is out the window, illegal, institutionalized criminality -- and certainly no bargain.
Buttons12, I was thinking the same thing. A plea is not evidence. Here's this from the American Bar Association:
Standard 14- 2.2. Withdrawn plea and discussions not admissible
(a) A plea of guilty or nolo contendere that has been withdrawn should not be admitted as evidence against the defendant in any criminal or civil action or administrative proceedings.
(b) Any statement made in the course of any proceedings concerning a plea of guilty or nolo contendere that has been withdrawn, or in plea discussions with the prosecuting attorney that result in a plea of guilty or nolo contendere that is later withdrawn, should not be admitted as evidence against the defendant in any criminal or civil action or administrative proceedings, except that such a statement may be admitted:
https://www.americanbar.org/groups/criminal_justice/publications/criminal_justice_section_archive/crimjust_standards_guiltypleas_blk/