Torture advocate John Yoo—who believes that the president has the legal power to order the testicle-crushing of a suspected terrorist's child and maybe even to suspend the First Amendment—believes that President Obama exceeded his power by saying he won't deport the children of illegal immigrants: "So what we have here is a president who is refusing to carry out federal law simply because he disagrees with Congress’s policy choices. That is an exercise of executive power that even the most stalwart defenders of an energetic executive — not to mention the Framers — cannot support."
This is actually completely consistent of Yoo, for one reason: President Obama didn't use "war" as the justification for the policy. But Yoo's history indicates there are virtually no limits on a president's powers if war-making is the justification. So Yoo would be conceivably be helpless—unless, of course, he's merely an opportunistic hack—if President Obama could justify his immigration decision in national security terms.
Let me offer one.
There is a national security concern that deporting young people—who, though they may not be actual citizens, have only known America as their home—to unfamiliar lands may radicalize them against the American government, a radicalization that, combined with their knowledge of the country and its customs, make them particularly useful allies to any terrorist organizations that wish to strike against us.
Now, I don't think there's much of a chance that would happen. But what's the old Dick Cheney standard? The One Percent Doctrine? This seems to fit that doctrine. And under Yoo's view of executive power, it's all the justification needed for President Obama's action. "War"—real or not—means never having to say you're sorry.