You know what his choice made me do? Donate to the EFF (they apparently even have a sponsor to match donations to $500k). I hope Mike realized how asinine his decision was.
Ignoring the moral aspects here, this is a smart strategic move. Who better to bring a case against bittorrent users than one who knows all their defensive moves?
From the other side, lawyers defending bittorrent users against Meier can use his old arguments against him. Though I don't know how much that will help.
From a lawyers perspective, this may even be admirable. part of the ethos of the industry is the ability to defend and prosecute both sides of an argument.
he's got more issues than just morality here, as the DC rules of professional conduct for lawyers apply to him..
in part, he may be barred (or may at least need consent) from any litigation where his new clients interests are adverse to his former clients interests.
For instance...
" a lawyer shall not represent a client with respect to a matter if:
(1) That matter involves a specific party or parties and a position to be taken by that client in that matter is adverse to a position taken or to be taken by another client in the same matter even though that client is unrepresented or represented by a different lawyer;
(2) Such representation will be or is likely to be adversely affected by representation of another client;"
It would be great if he turned out to have switched sides because he felt aggrieved and wronged by the people he used to defend, much like Benedict Arnold.
If you mean he can turn around and sue copyright trolls again, he cannot do that. His former clients will claim there is a conflict, since now he has access to their data under attorney client relationship.
i.e. the underlying problem, and the lawyer himself