http://www.supremecourt.gov/opinions/12pdf/11-345_l5gm.pdf
An applicant was denied admission to a university which uses race in admissions. The applicant is a white female, who would have been accepted if race hadn't been considered (ie, her other determining factors place her above students who were accepted, except they had slightly better overall score due to their race).
The Supreme Court accepted the case, and after deliberation determined that the lower courts hadn't shown that race is the only way to generate a diverse student body.
Essentially, insofar as I can tell, the ruling means race cannot be used to determine admission unless the university can show that there is no other way to create diversity in the student body.
Remember that the court already ruled on affirmative action in 2003 with
Grutter v. Bollinger, where the court ruled that a university does have a compelling interest in generating diversity on campus.
Two of the differences between the two cases are:
1.That case said "diversity is compelling" this case is asking, "is affirmative action the only way to generate diversity?"
2. A more conservative supreme court
We'll see if the university continues to press its case in the lower courts to prove that diversity can really only be generated through affirmative action.