The source (Legal dept) really doesn't matter, but the reasoning does. When the NBA, NCAA, then ACC Football all pulled out of NC because of the LGBT discrimination issues, that was the end of BYU's chance with the Big12. The President's of the Big12 Universities are not willing to risk the PR nightmare of welcoming in an institution with discriminatory policies (whether it is real or perceived). This is all about optics and the perception is that BYU discriminates against LGBT. None of those University Presidents is going to invest time in defending BYU, they have bigger fish to fry.