While the universities can completely do that, they can't get an antitrust exception while they do. That's the issue here, I think. The universities are colluding with one another as regards pricing and financial aid. This was allowed under an exception to antitrust law so long as financial aid played no role in admissions. The group is alleging that financial aid, or the lack of it, plays a role in admitting rich students. If that's the case, it's possible (but not anywhere close to certain) that the universities don't qualify for the antitrust exception.