I am not a lawyer Steve, but I read that a prosecution was being considered for the ex-cops.

Was it OK for Green to receive leaked documents

It is not illegal.

but not OK for the copper to leak his information?

That is illegal.

But if that policeman, properly or improperly, has exposed a sex pest, wouldn't that be mitigation?

He has not exposed a sex pest. If he is telling the truth he has exposed someone doing something perfectly legal that almost everyone has done, so no mitigation.

Questions, questions!

Yes, and no evidence so why are you still banging on about nothing?
It is just a politically motivated witch hunt.