If no one believes any law was broken, why is there still an ongoing investigation?
Because someone most probably lied and committed perjury in their testimony before the grand jury. It's the cover up that usually creates the problem. No one today is arguing the original disclosure was illegal except the totally uninformed or those who wish not to be informed. Miller is the one who is the key. She prefers a few months in jail to fingering one of her leftist presstitute pals.
If I understand this fisaco, the special prosecutor started down the road that linking Plame's name to Wilson's trip to Africa may (MAY) have been against 50 USC 421. As you note, if any one of those elements isn't there, then there is no violation of THAT statute.
But there would be obstruction of justice if any of the witnesses withheld or misrepresented evidence. Requiring testimony of Cooper and Miller may be required to reach a conclusion on a related charge.
The special prosecutor filed a paper with the court that said the primary investigation was concluded some time ago. But the issue of compelling the testimony of Cooper and Miller was unsettled until a recent SCOTUS ruling.