As with almost any lawsuit, battles over discovery, the legal right of  plaintiffs to demand and receive communications and other documents from the defendants (and vice versa), may become the first heart of the matter. The Epoch Times reports:

Roger Stone has announced that he will file a $25 million lawsuit against the Department of Justice (DOJ) while his lawyers file complaints for prosecutorial misconduct against a number of key DOJ officials. (snip)

"The terms of my pardon allow me to sue the Department of Justice, Robert Mueller, James Comey, John Brennan, Rod Rosenstein, Josnathan [sic] Kravis, Aaron 'Fat A**' Zelinsky, Jeannie Rhee, and Michael Morando," Stone posted to social media site Parler.

YouTube screen grab (cropped).

Details so far are sketchy:

The charges (pdf) were related to allegations that Stone had made false statements to the House Intelligence Committee during its probe of alleged Russian interference, and that he attempted to persuade a witness to give false testimony and withhold pertinent information from investigators.

Stone argued the judge in his case "hid exculpatory evidence" from his trial based on redacted sections of the Mueller report, "in which they admitted that they had no evidence whatsoever of my colluding with Russia, WikiLeaks, [or] Julian Assange."

The Mueller team from the start seemed to be composed of fanatical Trump-haters, and even though they are all lawyers, it is possible that, just like Peter Strzok and Lisa Page (both lawyers), they were injudicious in some of the internal communications.

I would expect the full panoply of excuses — especially classification — not to turn over internal communications will be employed by the defendants.  The DOJ has limitless resources to defend itself, and the Mueller team are experienced lawyers as well.

I wish Stone luck.  The Mueller team has been accused of many abuses, and I hope the individuals are somehow held accountable.