Balkinization last week had this impressive symposium on immigration and the President's enforcement discretion. Among the prominent commentators, of special note is Zachary Price: Two Cheers for the OLC Opinion (and again, here is his full-length scholarly article on the subject which has some important originalist arguments).
Without trying to be comprehensive, here are a couple of other good posts from varying perspectives –
Jack Goldsmith (Lawfare), The Immigration Imbroglio as (Pretty) Normal Separation of Powers (with this response at Opinio Juris by Gabor Rona [Cardozo law School]).
David Rivkin & Elizabeth Price Foley, Obama’s Immigration Enablers: The administration’s Office of Legal Counsel endorsed a view of executive power never imagined by the Founders.
At National Review, Josh Blackman, Obama's Unconstitutional Corner: His own Justice Department has provided an argument against him.
In their concluding essay on the Balkinization symposium, Adam Cox and Cristina Rodriguez say:
Posted at 6:43 AM