Although anyone can sue anyone for about anything. Regarding the issue of ninja mined coins, it is a controversy that might eventually go to court.
Keeping the tokens restricted instead of burned may be enough to keep a legal remedy in chancery instead of tort if he were to go after the witnesses. I am not a lawyer. I don't think that Justin sun would prevail in a tort or equity against the witnesses [other than to just scare them], expensive as it may be, if he were to target them given the obligations of the witnesses acting in good faith to protect the chain on top of all the abuses of Sun/Tron upon projects on the Tron chain, and the history of these ninja-mined coins and their intended uses.
If his goal is to do a swap to the tron chain, what would he do with his steem based coins? He would be destroying his own property, and ours too. His goals are to mint a new "steem" tron token of an unknown size, do a swap, an air drop, and the distribution is still an unknown. To him the value of a Steem coin is already zero. He can cook up as many Steem tron tokens as he wants, so him seeking a civil suit against anyone is almost a moot point. He can make Steemit operate on tron without a coin swap.
He should just take his steemit dapp, and part ways with Steem. But to do that he should consider suing Ned Scott.
If we suppose Justin sun purchased the Steem coin in good faith from steemit/ned scott and Justin Sun sued Ned Scott, Then I think this is the area where the steem community can move to defend Justin Sun's property. The ninja mined coins themselves was an act of fraud to begin with, Scott/steemit agreed to restrict their use to develop the community (exact wording needs research, including that they would not be used for voting for witnesses), and then he converted the fraudulently minted coins for his own gain to Justin Sun who threatens to destroy the chain itself which act as a breach of fiduciary value to the Steem community. It is quite possible Ned Scott lied to Justin sun about what he was getting into, just as Ned lied to the steem community. If Justin Sun wants to be made whole then it should be the duty of Ned Scott-not the steem community-to make him whole. The witnesses to defend Justin Sun's stake should be willing to file declarations/affidavits in an hypothetical (not all suits are ideal) Sun V Scott case asserting the bad faith and fraudulent conduct by Ned Scott/steemit.
It could be argued a large steem holder could file an injunction against Justin Sun/Tron/Jon Does from taking over the chain. Little people are expected to follow injunctions or else, big people find ways around them or outright defy them. Once the kill switch is thrown, whats the point of contempt of court. A case following in tort for damages might be settled; Paid in tron s___ coins probably.
Lots of possibilities..