Matier & Ross of the Chronicle break down the political barriers (both within MLB and the United States Congress) standing in the way of the team's move to San Jose here.
The piece is pretty interesting. Despite Matier & Ross' take, however, I'm not sure that Feinstein will care all that much -- especially after Oakland had 15 years to put something together and Dellums is just starting to make noise at the 11th hour.
The antitrust exemption for MLB is still a live-wire policy debate, but it's hard to imagine that a repeal would be evoked here. Neukom's gripe would essentially be that he has territorial rights that he wants to enforce, and that the A's move to San Jose would hinder the Giants' ability to cash in on those territorial rights. That sounds like he's trying to keep competition at arm's length; not exactly the argument you topple an antitrust exemption with. If anything, the squashing of the 1992 Giants sale to the Tampa group would have been closer to an ideal case with which to challenge the antitrust exemption head-on.
That being said, Neukom does come from a big-guns legal background, so a lawsuit under any theory coming from him and his team of attorneys could be pretty scary.
All of that aside, I would bet Selig could line up support amongst the owners. No owner wants to set precedent for being pinned down to a stadium they don't want, and there is already precedent for moving into another team's territory with the Washington Nationals camping out in the Baltimore Orioles' backyard...still, it's a potentially hairy situation.
What I find interesting is that Matier & Ross didn't touch on political forces that stand in the way of the move stemming from San Jose; even if you have the mayor and some city council members on board, there's no guarantee that San Jose voters would approve a deal. In this economy, I wouldn't be surprised if even the most exciting projects that carry potential debt loads came under serious attack locally.