This is not a case of theft.

This is a case of murder.
Old STEEM was killed by Mr. Tron.

Now we have two new block chains STEEM(justin) and HIVE

the only confusion is that Mr. Tron kept the old name.

And any lawsuit would be dead in the water.
Sure they could prove damages in a securities fraud case, but all that can be attached is the empty shell that is steemit inc.

In order to go after Mr. Tron, you would need to get him inside a proper jurisdiction (really difficult) and then PROVE that he is the owner of said keys (an almost impossible task). Sure we all know that those are Mr. Tron's keys, but we really have never seen them in his possession. We can only prove that they existed in the past.