It's not a line-item veto. That wiki page mentions it has not become law. As far as I can tell, the bill is in committee. Both the House and Senate have to vote on the exact same bill. But both houses like to make their own changes. So each pass their own version of the bill, then meet in committee to come up with a version they both agree on, this new one goes back to both houses and they pass it. What I suspect is being claimed is that it says "shareholders" in both the House and Senate versions that already passed, and the White House is asking the committee to change that to "shareholder", otherwise Obama will veto it.

Edit: This article contains a barely legible image describing the process: http://www.mcclatchydc.com/2010/03/03/89797/heres-how-reconc...

I did remember that the '96 act was axed by the court, but I wasn't aware of the more recent versions. I suppose this story is a perfect demonstration of why this kind of thing is a bad idea

That's just plain wrong. There is no federal line item veto and even if there were you couldn't use it to veto one letter.

I realized that after the fact. I guess when I heard about it in history class, it existed, then I inquired further.