A report from the Waco Tribune says that Baylor and the other schools currently blocking Texas A&M's Big 12 exit are not really trying to prevent A&M from leaving. It's really all about Oklahoma:

If Oklahoma reaffirms its commitment to the Big 12, the schools are expected to sign the waiver that would allow the Aggies to go to the SEC without any legal action. The Sooners, who are reportedly considering a move to the Pac-12, are expected to make their decision within the next two weeks.

A few weeks ago (maybe a month, I can't remember at this point), the general feeling became that the Big 12 would continue with nine teams and maybe add a tenth if Texas A&M left. Two things have happened since then. First, the pie-in-the-sky expansion candidates (Notre Dame and Arkansas) declined, and the rest of the Big 12 figured out that they weren't getting anyone better than maybe BYU or more likely TCU or Houston. Second, Oklahoma became extremely vocal in insisting that it would explore all of its options. The Big 12 can survive as a BCS automatic qualifier without Texas A&M, but it can't without Oklahoma.

The non-power schools are basically using the only scrap of leverage they have left to try to keep the conference together. They're trying to slow things down and extract a pledge from Oklahoma that it will give the Big 12 without A&M a try before bolting to the Pac-12. I doubt they think that legal threats will keep OU in the conference; it's all about buying time.

It's likely a fool's errand though. Texas A&M committed to the Big 12 last summer, and look where we are now. If OU wants to go, nothing it commits to in the next few days will ultimately stop it from leaving.

UPDATE

Travis Haney reports that an Oklahoma official hasn't heard anything about this. Who knows what's actually going on, but there's your denial from OU.