The Justice Department's memorandum on deferring deportation of some categories of illegal aliens
If you're interested, here's the Justice Department Office of Legal Counsel's opinion titled, "The Department of Homeland Security's Authority to Prioritize Removal of Certain Aliens Unlawfully Present in the United States and to Defer Removal of Others", released yesterday. I'd be happy to add links to any detailed legal analyses on the other side. (This isn't my area of expertise, so I can't opine confidently on the arguments myself.)
UPDATE: Prof. Josh Blackman has a detailed analysis.