"al-Kidd v. Ashcroft: Is Pretextual Use of the Material Witness Statute Unconstitutional?"

That's the title of Orin Kerr's helpful post over at The Volokh Conspiracy. The bottom line(s) (after substantial analysis):

First, the rejection of absolute immunity seems right. Second, the Fourth Amendment holding seems possible but rather unlikely, and in general misses the key legal question raised by the case. Third, I think the qualified immunity analysis is clearly incorrect.