For an overview of President Obama's deferred action programs for certain noncitizens, currently under threat of being revoked by President Trump:
A discussion of DACA/DAPA as an exercise of positive discretion:
The following short articles provide analysis of some possible limits to the interior enforcement executive actions from various perspectives:
Ali v. Trump, No. 2:17-cv-00135 (Western District of Washington, filed Jan. 30, 2017).