Salon interviews Jonathan Turley, a law professor:
What's interesting is Holder's statement that the department will work closely with the courts to ensure that Congress has a fair and full opportunity to participate in pending litigation. That would seem to mean that the Justice Department will support a special counsel to defend these laws in support of Congress. That will create a situation where you have one lawyer representing the legislative branch and arguing in favor of constitutionality, and another lawyer representing the executive branch and arguing against constitutionality.
But he rightly doesn't expect this to make a huge difference, for all the hyper-ventilation on both sides:
I should note, though, that if this were to go to the Supreme Court, I do not expect that the position of the administration would necessarily sway any justices. The justices are likely to have very clear views on the constitutionality of this question. Justice Scalia recently talked publicly about the limits of the Equal Protection Clause. But it certainly adds more support to the challenges going forward. It never hurts to have the executive branch on your side.