Obama's Executive Order on Immigration: Is it Legal?

Although I favor comprehensive immigration reforms, including relief for many of those persons living and working in the United States in an undocumented status, I think the President unconstitutionally crossed the line between prosecutorial discretion (an Executive function) and policy making (a legislative function) when he signed an Executive Order, which will allow several million undocumented persons to remain in the United States.  For my reasoning, see this post on Aleteia.